Long-term implications of feed energy source in different genetic types of reproductive rabbit females: III. Fitness and productivity

The specialization process associated with genetic selection could be associated with functional disorders, affecting the reproductive success of females (fitness). We hypothesized that by modulating energy acquisition and allocation of females we could balance productivity and reproductive success. To test this hypothesis, we used 203 rabbit females belonging to three genetic types: H (n=66) maternal line specialized in prolificacy, LP (n=67) generalist maternal line, R (n=70) paternal line specialized in growth rate. We fed each genetic type with two diets specifically designed to promote milk yield (AF) or body reserves recovery (CS). We controlled females between their first and fifth reproductive cycles, recording traits related with productivity and fitness of females. H females fed CS had on average 11.2±0.43 kits with an individual weight of 54±1.2 g at birth and 525±11 g at weaning. Their conception rate when multiparous was 44% and their survival rate at the end of the experiment 30%. When they were fed AF, the individual weight of kits was 3.8 g heavier (P<0.05) at birth and 38 g heavier at weaning (P<0.05), the conception rate when multiparous increased 23 percentage points (P<0.05) and the survival rate at the end of the experiment 25 percentage points (P<0.05). LP females fed CS had on average 10.8±0.43 kits with an individual weight of 52±1.2 g at birth and 578±11 g at weaning. Their conception rate when multiparous was 79% and their survival rate at the end of the experiment 75%. When they were fed AF, it only increased individual weight of kits at weaning (+39 g; P<0.05). R females fed CS had on average 8.4±0.43 kits with an individual weight of 60±1.2 g at birth and 568±11 g at weaning. Their conception rate when multiparous was 60% and their survival rate at the end of the experiment 37%. When they were fed AF, they presented 1.4 kits less at birth (P<0.05) but heavier at birth (+4.9 g; P<0.05) and at weaning (+37 g; P<0.05). Therefore, we observed that genetic types prioritized different fitness components and that diets could affected them. In this sense, seems that more specialized genetic types, were more sensitive to diets than the more generalist type.     

Environmental sensitivity differs between rabbit lines selected for reproductive intensity and longevity

To better understand the mechanisms that allow some animals to sustain their productive effort in harsh environmental conditions, rabbit does from two selection lines (LP and V) were housed in normal (NC), nutritional (NF) or heat (HC) challenging environmental conditions from first to third partum. The LP line (n=85) was founded on reproductive longevity criteria by selecting does from commercial farms that had a minimum of 25 partum with more than 7.5 kits born alive per parity. Line V (n=79) was constituted from four specialised maternal lines into a composite synthetic line and then selected by litter size at weaning for 36 generations. Female rabbits in NC and NF environments were housed at normal room temperature (18°C to 24°C) and fed with control [11.6 MJ digestible energy (DE)/kg dry matter (DM)] or low-energy diets (9.1 MJ DE/kg DM). HC does were housed at high room temperatures (25°C to 35°C) and fed the control diet. Female rabbits in the HC and NF environments ingested 11.5% and 6% less DE than NC does, respectively (P<0.05). These differences between environments occurred in both lines, with the differences being higher for LP than for V does (+6%; P<0.05). Milk yield responses followed those of energy intake also being higher for LP does (+21.3 g/day; P<0.05). The environmental conditions did not affect the perirenal fat thickness (PFT), but a genotype by environment interaction was observed. In NC and HC, the PFT was higher for line V (+0.23 and +0.35 mm, respectively; P<0.05) than for LP does, but this was not the case at NF (−0.01 mm). Moreover, the PFT evolution was different between them. In the NC environment, LP does used the accreted PFT in late lactation (−0.29 mm), whereas V does did not (−0.08 mm). Conversely, in the HC environment, LP does showed a flat PFT evolution in late lactation, whereas V does accumulated PFT. In the NF environment, LP and V does had a similar PFT evolution. There was also a litter size reduction for V does of −2.59 kits total born in HC and −1.78 kits total born in NF environments, whereas this was not observed for LP does. The results for LP does indicate a direct use of DE ingested for reproduction with little PFT change, whereas V does actively use the PFT reserves for reproduction.     

Differences in productive robustness in rabbits selected for reproductive longevity or litter size

The aim of this work was to evaluate the ability of a line selected for reproductive longevity (LP) to confront productive challenges compared to a line selected during 31 generations for litter size at weaning (V). A total of 133 reproductive rabbit does were used (72 and 61 from LP and V lines, respectively). Within each line, three groups with different levels of productive effort were planned: PP9, inseminated at day 4 after the first partum and with nine kits during the second partum, and inseminated after first weaning (30 days) and with nine (PW9) or five kits (PW5) during the second partum. The reproductive performance, body condition (perirrenal fat thickness (PFT)) and lipolytic response were controlled. LP does showed greater mean live weight (LW; +128 g; P < 0.05), PFT (+0.47 mm; P < 0.05) and estimated body energy (EBE; +0.29 MJ/kg; P < 0.01) than V does at second partum. However, LP does that mated at first post partum did not significantly differ in EBE relative to V does at second partum. During the first week of lactation, dry matter (DM) intake was similar for both lines (94 and 95 g DM/kg LW0.75 day for V and LP does, respectively). There was a significant difference in milk yield between both lines during the first week when litter size was nine (60 v. 54 g of milk/kg LW0.75 day for LP and V does, respectively; P < 0.01), but no difference when litter size was five. Consequently, when litter size was nine, LP does showed a lower recovery of PFT (0.6 mm less; P < 0.05) than V does during the first 10 days of lactation. However, when litter size was five, LP does showed a higher LW (+210 g; P < 0.05) than V does at 10 days of lactation and a similar recovery of PFT. During the last 3 weeks of the lactation, LP does showed a higher feed intake (+6 g DM/kg LW0.75 day; P < 0.05) and milk yield (+27 g/day; P < 0.001) than V does when litter size was nine, resulting in no significant differences in LW at 30 days of lactation. However, when litter size was five, both lines showed similar feed intake and milk yield, maintaining their differences in LW at 30 days of lactation (+206 g for LP does; P < 0.05). These results show that the rabbit line selected for reproductive longevity is more robust with respect to coping with productive challenges, than a line selected for reproductive intensity.     

Consequences of rearing feeding programme on the performance of rabbit females from 1st to 2nd parturition

To evaluate how rearing programmes could affect resources allocation and reproductive performance of primiparous rabbit females, a total of 118 rabbit females were used to evaluate the effects of five rearing feeding programmes on their performance from 1st to 2nd parturition: CAL, fed ad libitum C diet (11.0 MJ digestible energy (DE), 114 g digestible protein (DP) and 358 g NDF/kg dry matter (DM) until 1st parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until 1st parturition; F, fed ad libitum with F diet (8.7 MJ DE, 88 g DP and 476 NDF/kg DM) until 1st parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until 1st parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until 1st parturition. From 1st parturition, C diet was ad libitum offered to all the experimental groups until 2nd parturition. CAL females presented lower feed intake than females of F, FC and FCF groups in the 1^st week of lactation (on av. −16.6%; P<0.05). During 1st lactation, the perirenal fat thickness change in CAL females was not different from 0 (+0.02 mm), while in the other four groups it increased (on av. +0.44 mm; P<0.05). Plasma of females fed with F diet during rearing (F, FC and FCF) had lower non-esterified fatty acids content than those exclusively fed with C diet (–0.088 and –0.072 mmol/l compared to CAL and CR, respectively; P<0.05). FCF litters had higher weight than F litters at day 21 of lactation (+247 g; P<0.05), but FCF litter had significantly lower weight than FC litters at weaning (+170 g; P<0.05). CR females had the shortest average interval between the 1st and 2nd parturition (49 days) and FCF females the longest (+ 9 days compared to CR; P<0.05). At 2nd parturition, liveborn litters of F females were larger and heavier than litters of FCF females (+2.22 kits and +138 g; P<0.05), probably due to the lower mortality at birth of F litters (–16.5 percentage points; P<0.05). In conclusion, rearing females on fibrous diets seems to increase the ability of primiparous rabbit females to obtain resources, especially at the onset of lactation.     

Long-term implications of feed energy source in different genetic types of reproductive rabbit females. II. Immunologic status

Genetic selection and nutrition management have played a central role in the development of commercial rabbitry industry over the last few decades, being able to affect productive and immunological traits of the animals. However, the implication of different energy sources in animals from diverse genetic lines achieving such evolutionary success remains still unknown. Therefore, in this work, 203 female rabbits housed and bred in the same conditions were used from their first artificial insemination until their fifth weaning. The animals belonged to three different genetic types diverging greatly on breeding goals (H line, hyper-prolific (n=66); LP line, robust (n=67) and R line, selected for growth rate (n=67), and were assigned to two experimental diets, promoting major differences in energy source (cereal starch or animal fat)). The aims of this work were to: (1) characterize and describe blood leucocyte populations of three lines of rabbit does in different physiological stages during their reproductive period: first artificial insemination, first weaning, second parturition and fifth weaning; and (2) study the possible influence of two different experimental diets on the leucocyte populations in peripheral blood. Flow cytometry analyses were performed on blood samples taken from females at each different sampling stade. Lymphocyte populations at both weanings were characterized by significantly lower counts of total, CD5⁺ and CD8⁺ lymphocytes (–19.8, –21.7 and –44.6%; P<0.05), and higher counts of monocytes and granulocytes (+49.2 and +26.2%; P<0.05) than in the other stages. Females had higher blood counts of lymphocytes B, CD8⁺ and CD25⁺ and lower counts of CD4⁺ at first than at fifth weaning (+55.6, +85.8, +57.5, –14.5%; P<0.05). G/L ratio was higher at both weanings (P<0.05), and CD4⁺/CD8⁺ ratio increased progressively from the 1AI to the 5 W (P<0.001). Regarding the effect of genetic type in blood leucocyte counts, LP animals presented the highest counts for total, B, CD5⁺ and CD8⁺ lymphocytes (+16.7, +31.8, +24.5 and +38.7; P<0.05), but R rabbits showed the highest counts for monocytes and granulocytes (+25.3 and +27.6; P<0.05). The type of diet given during the reproductive life did not affect the leucocyte population counts. These results indicate that there are detectable variations in the leucocyte profile depending on the reproductive stage of the animal (parturition, weaning or none of them). Moreover, foundation for reproductive longevity criteria allows animals to be more capable of adapting to the challenges of the reproductive cycle from an immunological viewpoint.     

Safflower seeds in corn silage and alfalfa hay based early lactation diets: A practice within an optimum forage choice

Safflower seed (SS), Carthamus tinctorius L., has the highest concentration of linoleic acid among 80 oilseeds. It was hypothesized that an Iranian variety of SS can be effectively fed with cottonseeds (CS) to maintain feed intake, energy metabolism and productivity of early lactation cows under negative energy balance. Our objective was to determine effects of feeding diets containing 100 g whole CS with (1) no SS (SS0), (2) 75 g CS + 25 g SS (SS25), or (3) 50 g CS + 50 g SS (SS50), per kg of dietary DM, on feed intake, rumen fermentation, blood metabolites and milk production of early lactation cows fed diets based on a uniform mixtures of alfalfa hay and corn silage. Nine multiparous early lactation Holstein cows (46 ± 7 d in milk) were used in a replicated 3 × 3 Latin square design study with three 21-d periods. Each period had 14 d of adaptation and 7 d of data collection. Dietary inclusion of SS did not affect (P>0.10) DM intake, rumen pH and concentrations of ammonia and VFA, blood concentrations of insulin, non-esterified fatty acids, urea and triglycerides, and milk production. Adding SS linearly reduced blood glucose (P=0.05) and beta-hydroxybutyric acid (P<0.05), and increased blood total cholesterol (P<0.01) and low-density lipoproteins (P<0.05) concentrations. Results demonstrated that SS as an economical and rich source of essential fatty acids can be included up to 50 g/kg of dietary DM alongside CS for early lactation cows without affecting feed intake while maintaining rumen fermentation, peripheral energy supply and milk production.     

Effects of feeding programme on the performance and energy balance of nulliparous rabbit does

A total of 190 rabbit females were used to evaluate five feeding programmes from 9 weeks of age to the first parturition: CAL, fed ad libitum with a control diet (C: 11.0 MJ digestible energy (DE) and 114 g digestible protein (DP)/kg dry matter (DM)) until first parturition; CR, fed ad libitum with C diet until 12 weeks of age and then C diet restricted (140 g/day) until first parturition; F, fed ad libitum with a low-energy, high-fibre diet (F: 8.7 MJ DE and 88 g DP/kg DM) until first parturition; FC, fed with F diet ad libitum until 16 weeks of age, and C diet ad libitum until first parturition; FCF, fed with F diet ad libitum until 16 weeks of age, then C diet ad libitum until 20 weeks and then F diet ad libitum until first parturition. The rabbits were artificially inseminated at 18 weeks of age. CAL group had a higher mortality rate compared with the other groups between 9 and 12 weeks of age (34% v. 3%; P < 0.05) and during the last 3 weeks of first pregnancy (14% v. 3%; P < 0.05). The CAL and FC females presented higher BW and perirenal fat thickness (PFT) than CR females at 11 days of pregnancy (+0.41 kg and +0.6 mm; P < 0.05), with F females showing medium values. The type of feeding procedure did not affect the fertility rate of young females at first artificial insemination. Differences in BW disappeared at parturition, when only CAL females presented a greater PFT than CR and FC females (+0.3 mm; P < 0.05). In comparison with FCF, CAL females had smaller and thinner live born litters (−2.5 kits and −139 g, respectively; P < 0.05), with CR, F and FC females showing medium values. The low number of kits born alive for CAL females was because of their lesser total number of kits born (−1.7 kits; P < 0.05) and the greater mortality of their litters at birth (+13.9%; P < 0.05) compared with FCF females. Non-esterified fatty acid was higher in the blood of females fed C diet (CAL and CR) than in others at partum day (on average +0.15 mmol/l; P < 0.05). In conclusion, the ad libitum use of diets for lactating rabbit does throughout the rearing period could lead young rabbit females to present a higher risk of early death and smaller litter size at first parturition. Feed restriction or earlier use of suitably fibrous diets led females to achieve the critical BW and fat mass at first mating to ensure reproduction.     

Impact of fat source and dietary fibers on feed intake,plasma metabolites,litter gain and the yield and composition of milk in sows

Sow lactation diets often include fat sources without considering the impact on digestion, metabolism and performance. Fiber ingredients may reduce feed intake and are often completely excluded from lactation diets, although locally available ingredients may be cost-efficient alternatives to partly replace cereals in lactation diets. Thus, a standard lactation diet low in dietary fiber, and two high-fiber diets based on sugar beet pulp (SBP) or alfalfa meal (ALF) were formulated. The SBP diet was high in soluble non-starch polysaccharides (NSP), whereas ALF being high in insoluble NSP. Each diet was divided in three portions and combined with 3% soybean oil (SOYO), palm fatty acid distillate (PFAD), or glycerol trioctanoate (C8TG) as the dietary fat source. Equal amounts of metabolizable energy were fed to 36 second parity sows from day 105 of gestation and throughout lactation to study the impact on feed intake, plasma metabolites, milk production and litter performance. Backfat thickness and BW of sows were recorded on days 3, 17 and 28 of lactation; blood was sampled on days 3 and 17; milk samples were obtained on days 3, 10, 17 and 24 of lactation; and piglets were weighed on days 2, 7, 14, 21 and 28 of lactation. Litter gain and milk yield during late lactation were greater in sows fed C8TG or SOYO than in sows fed PFAD (P=0.05), whereas loss of BW (P=0.60) and backfat (P=0.70) was unaffected by fat source. Milk protein on days 3 and 10 of lactation were lower in C8TG and SOYO sows, than in PFAD sows (P<0.05). The lowest concentration of plasma lactate on day 3 (P<0.05) and plasma acetate on day 17 (P<0.05) was observed in C8TG sows. Milk yield was unaffected by fiber treatment (P=0.43), whereas milk protein concentration was lowest in ALF sows (P<0.05). Feed intake tended to be lower (P=0.09), and litter gain during the 3^rd week of lactation was decreased (P<0.05) in SBP sows. In conclusion, performance was enhanced in SOYO and C8TG compared with PFAD sows, possibly associated with reduced energy intake in PFAD-fed sows. Furthermore, the SBP diet seemed to impair feed intake and litter gain at peak lactation, suggesting that effects of the dietary fiber fraction on energy intake determines the potential inclusion level of fiber-rich ingredients.     

Feeding corn grain steeped in citric acid modulates rumen fermentation and inflammatory responses in dairy goats

Cereal grains treated with organic acids were proved to increase ruminal resistant starch and can relieve the risk of ruminal acidosis. However, previous study mainly focussed on acid-treated barley, the effects of organic acid-treated corn is still unknown. The objectives of this study were to evaluate whether feeding ground corn steeped in citric acid (CA) would affect ruminal pH and fermentation patterns, milk production and innate immunity responses in dairy goats. Eight ruminally cannulated Saanen dairy goats were used in a crossover designed experiment. Each experimental period was 21 day long including 14 days for adaption to new diet and 7 days for sampling and data collection. The goats were fed high-grain diet contained 30% hay and 70% corn-based concentrate. The corn was steeped either in water (control) or in 0.5% (wt/vol) CA solution for 48 h. Goats fed CA diet showed improved ruminal pH status with greater mean and minimum ruminal pH, and shorter (P<0.05) duration of ruminal pH<5.6 and less area of ruminal pH<5.6, 5.8 and 6.0. Concentration of total volatile fatty acid and molar proportion of propionate were less but the molar proportion of acetate was greater (P<0.05) in goats fed the CA diet than the control diet. Concentration of ruminal lipopolysaccharide (LPS) was lower (P<0.05) and that of lactic acid also tended (P<0.10) to be lower in goats fed CA than the control. Although dry matter intake, actual milk yield, yield and content of milk protein and lactose were not affected, the milk fat content and 4% fat-corrected milk tended (P<0.10) to be greater in goats fed CA diet. For the inflammatory responses, peripheral LPS did not differ, whereas the concentration of LPS binding protein and serum amyloid A tended (P<0.10) to be less in goats fed CA diet. Similarly, goats fed CA diet had less (P<0.05) concentration of haptoglobin and tumour necrosis factor. These results indicated that feeding ground corn treated with CA effectively improved ruminal pH status, thus alleviated the risk of ruminal acidosis, reduced inflammatory response, and tend to improve milk yield and milk fat test.     

Heritability and repeatability of milk lactose and its relationships with traditional milk traits,somatic cell score and freezing point in Holstein cows

Lactose percentage (LP) in milk is currently determined in most herd-testing schemes, and globally, it is usually routinely recorded in the framework of the official milk recording procedures. However, few studies have investigated the phenotypic and genetic variability of this component. Data used in the present paper consisted of 59 811 test-day records from 4355 Holstein cows in 266 herds. Heritabilities of LP and lactose yield (LY) were estimated through single-trait repeatability animal models, whereas genetic and phenotypic correlations of LP and LY with milk composition and production traits, somatic cell score and milk freezing point were estimated using bivariate models. Fixed effects included in the analyses were herd-test-date, season of calving, parity, stage of lactation and the interaction between parity and stage of lactation. Random effects were animal additive genetic, within and across lactation permanent environment and the residual. Lactation curves of LP and LY increased from parturition to the peak of lactation and decreased thereafter, mirroring the typical curve of milk yield. Lactose percentage was greater in first- than later-parity cows. Heritabilities of LP and LY were 0.43±0.03 and 0.14±0.02, respectively, and LP and protein percentage were the most repeatable traits. Genetic correlations (r_a) of LP with somatic cell score, LY and milk freezing point were −0.22±0.08, 0.28±0.08 and −0.46±0.05, respectively. Genetic relationships of LY with milk yield (r_a=0.97±0.00), fat percentage (r_a=−0.71±0.06), protein percentage (r_a=−0.57±0.06) and protein yield (r_a=0.64±0.06) were moderate to strong. Results suggest that milk LP could be considered in breeding strategies to accelerate the gain of correlated low heritable traits. Further research is needed to evaluate the feasibility of including LP in the selection index of Italian Holstein population to address country-specific needs and market demands.     

Effect of feeding protected fat and proteins on milk production,composition and nutrient utilization in Murrah buffaloes (Bubalus bubalis)

Objective of this study was to investigate the effect of feeding protected fat and proteins on milk production, composition and nutrient utilization in Murrah buffaloes (Bubalus bubalis). Eighteen buffaloes were divided into two groups (9 each) on the basis of most probable production ability. Buffaloes in control group (C group; most probable production ability 2204 kg) were fed chaffed wheat straw, chopped maize fodder and concentrate mixture as per requirements. Buffaloes in supplemented group (S group; most probable production ability 2211 kg) were fed same ration as C group plus 2.5% rumen protected fat (on dry matter intake basis) and formaldehyde treated mustard and groundnut oil cake (1.2 g formaldehyde/100 g crude protein) in place of unprotected cakes. Group S buffaloes were supplemented rumen protected fat and protein 60 days pre-partum to 90 days postpartum and persistence of milk production was monitored up to 210 days of lactation. Milk yield during supplementation period (90 days) in S group was 13.11 kg/d and was 19% higher (P<0.01) than the C group (11.01 kg/d), whereas after supplement withdrawal (120 days), it was 11.04 kg/d and was 15% higher (P<0.01) than the C group (9.61 kg/d). There was no effect on total solid, protein, solid-not fat (SNF) and lactose contents in the two groups, whereas milk fat yield was increased (P<0.05) and level of milk urea nitrogen was decreased (P<0.01) in S group. Moreover, the supplement produced noticeable changes in the fatty acid profile of the milk fat, i.e., reduction in the concentration of saturated fatty acids (SFA) by 19% and an increase in that of unsaturated fatty acids (USFA) by 36%. Besides, digestibility of dry matter, crude protein, acid detergent fiber and neutral detergent fiber were not affected, whereas ether extract digestibility was higher (P<0.05) in S group. There was no effect on plasma glucose, non-esterified fatty acids, triglycerides and cholesterol concentrations between two groups, whereas blood urea nitrogen concentration was lower (P<0.01) in S group. Supplementation of protected nutrients to buffaloes increased milk production and unsaturated fatty acids content in milk fat and persistence of lactation after supplements were withdrawn.     

Dietary supplementation with maize distillers dried grains with solubles during late gestation and lactation: Effects on sow and litter performance,and on colostrum and milk composition

The objectives of this study were to determine the effects of maize distillers dried grains with solubles (DDGS) during late gestation and lactation on sow and piglet performance, and on colostrum and milk composition. Thirty-six second- and third-parity (2.43 parity) sows (Yorkshire) were allotted to 1 of 3 groups and fed diets containing 0 (control), 200 or 400 g DDGS/kg during the last 20 d of gestation and throughout a 21 d of lactation. Experimental diets contained 12.9 MJ metabolizable energy/kg and 9.7 g lysine/kg. The colostrum and milk samples were obtained on d 0 (farrowing) and d 21 (weaning). There were no differences (P>0.05) in the sows’ average gestation lengths, weaning-to-estrus interval, average daily feed intake, and the lactation backfat and body weight change between dietary treatments. There were no dietary effects (P>0.05) of DDGS on the numbers of total, born alive piglets, average birth weights, piglets per litter at weaning or piglets average daily gain during lactation. No differences (P>0.05) were observed in total solids, protein, fat and lactose among the sows fed the DDGS diets compared with the control. The composition of total solids and protein of sows colostrum and milk were higher at farrowing (d 0) than at weaning (d 21) (P<0.001). However, the fat and lactose content of sows colostrum and milk were increased (P<0.001) from d 0 (farrowing) to d 21 (weaning). In conclusion, the results suggest that 400 g DDGS/kg (87 g lysine/kg) supplemented with 5.2 g lysine/kg included in late gestation and lactation diets is sufficient to replace all the dietary soybean meal without significantly affecting sow and litter performance or colostrum and milk composition.     

Evaluation of production efficiencies at pasture of lactating suckler cows of diverse genetic merit and replacement strategy

Feed costs account for the largest proportion of direct cost within suckler beef production systems. By identifying the cow type with enhanced capability of converting grazed herbage to beef output across lactations, suckler cow systems would become more efficient and sustainable. The objective of this study was to estimate grass DM intake (GDMI) and production efficiency among lactating suckler cows of diverse genetic merit for the national Irish maternal index (Replacement Index) which includes cow efficiency components such as milk yield and feed intake. Data from 131 cows of diverse genetic merit within the Replacement Index, across two different replacement strategies (suckler or dairy sourced), were available over two grazing seasons. Milk yield, GDMI, cow live weight (BW) and body condition score (BCS) were recorded during early, mid and late-lactation, with subsequent measures of production efficiency extrapolated. Genetic merit had no significant effect on any variables investigated, with the exception of low genetic merit (LOW) cows being 22 kg heavier in BW than high genetic merit (HIGH) cows (P < 0.05). Beef cows were 55 kg heavier in BW (P < 0.001), had a 0.31 greater BCS (P < 0.05) and 0.30 Unité Fourragère Lait (UFL) greater energy requirement for maintenance compared to dairy sourced beef × dairy crossbred (BDX) cows (P < 0.001). The BDX had 0.8 kg greater GDMI, produced 1.8 kg more milk (P < 0.001), had a 0.8 UFL greater energy requirement for lactation and produced weanlings that were 17 kg heavier in BW than beef cows (P < 0.05). Subsequent efficiency variables of milk per 100 kg BW (P < 0.001), milk per kg GDMI (P < 0.001) and GDMI per 100 kg BW (P < 0.001) were more favourable for BDX. The correlations examined showed GDMI had moderate positive correlations (P < 0.001) with intake per 100 kg BW, net energy intake per kg milk yield, RFI and intake per 100 kg calf weaning weight but was weakly negatively correlated to milk yield per kg GDMI (P < 0.001). No difference was observed across genetic merit for beef cows for any of the traits investigated. Results from the current study showed that, while contrasting replacement strategies had an effect on GDMI and production efficiency, no main effect was observed on cows diverse in genetic merit for Replacement Index. Nonetheless, utilising genetic indexes in the suckler herd is an important resource for selecting breeding females for the national herd and phenotypic performance generated from this study can be included in future genetic evaluations to improve reliability of genetic values.     

Genetic and phenotypic correlations among feed efficiency,production and selected conformation traits in dairy cows

The difficulties and costs of measuring individual feed intake in dairy cattle are the primary factors limiting the genetic study of feed intake and utilisation, and hence the potential of their subsequent industry-wide applications. However, indirect selection based on heritable, easily measurable, and genetically correlated traits, such as conformation traits, may be an alternative approach to improve feed efficiency. The aim of this study was to estimate genetic and phenotypic correlations among feed intake, production, and feed efficiency traits (particularly residual feed intake; RFI) with routinely recorded conformation traits. A total of 496 repeated records from 260 Holstein dairy cows in different lactations (260, 159 and 77 from first, second and third lactation, respectively) were considered in this study. Individual daily feed intake and monthly BW and body condition scores of these animals were recorded from 5 to 305 days in milk within each lactation from June 2007 to July 2013. Milk yield and composition data of all animals within each lactation were retrieved, and the first lactation conformation traits for primiparous animals were extracted from databases. Individual RFI over 301 days was estimated using linear regression of total 301 days actual energy intake on a total of 301 days estimated traits of metabolic BW, milk production energy requirement, and empty BW change. Pair-wise bivariate animal models were used to estimate genetic and phenotypic parameters among the studied traits. Estimated heritabilities of total intake and production traits ranged from 0.27±0.07 for lactation actual energy intake to 0.45±0.08 for average body condition score over 301 days of the lactation period. RFI showed a moderate heritability estimate (0.20±0.03) and non-significant phenotypic and genetic correlations with lactation 3.5 % fat-corrected milk and average BW over lactation. Among the conformation traits, dairy strength, stature, rear attachment width, chest width and pin width had significant (P<0.05) moderate to strong genetic correlations with RFI. Combinations of these conformation traits could be used as RFI indicators in the dairy genetic improvement programmes to increase the accuracy of the genetic evaluation of feed intake and utilisation included in the index.     

Maize silage and whole maize plant pellets as the basic forages in complete feeds for milk cows

A long-term experiment with twenty-one Ayrshire cows in their third lactation compared traditional (seasonal) feeding with complete diets based on maize silage or on maize plant pellets, each in combination with lucerne pellets.During the first experimental lactation cows fed on the traditional diet produced the least milk. Cows of the silage group had 9% more fat corrected milk (p > 0.05) than the other two groups and produced 191 kg butterfat compared with 176 and 175 kg for the control and maize pellets groups.During the second experimental lactation the milk yield of the cows fed on dehydrated maize pellets decreased dramatically owing to chronic bloating in one cow and refusals of pellets in the others for some periods of time. The maize silage group gave 5818 kg 4% fat-corrected milk compared with 4781 kg (p<0.05) and 4031 kg (p<0.001) for the control and maize pellets groups, respectively. A maize silage diet given throughout the year was the most profitable. The diet containing whole maize plant pellets was not economically competitive even when used temporarily.     

Effect of feed restriction or feeding high-fibre diet during the rearing period on body composition, serum parameters and productive performance of rabbit does

This study evaluated the effect of different feeding regimes from 11 weeks of age to first parturition on feed intake, leptin, non-esterified fatty acids (NEFA) and total protein serum levels, as well as productive performance in young rabbit does. In addition, body composition was estimated by bioimpedance analysis. Thirty-six 11-week-old does were randomly distributed in three groups. The AL-C group was fed ad libitum a control diet containing 350 g neutral detergent fibre (aNDFom)/kg, 11.6 MJ digestible energy (DE)/kg and 173 g crude protein (CP)/kg, and the does were inseminated at 16 weeks of age. The R-C group was fed 150 g/d of the same diet until 16 weeks of age, one week before artificial insemination (AI) at 17 weeks of age, and then fed ad libitum. The AL-F group was fed a diet containing 475 g aNDFom/kg, 9.4 MJ DE/kg and 174 g CP/kg ad libitum, and was inseminated at 17 weeks of age. During rearing (11-16 weeks), does in the R-C group had the lowest DE (1.54 MJ/d; P<0.003) and digestible protein (DP, 17.9 g/d; P<0.001) intake, as well as the lowest protein (172 g/kg; P<0.05) and energy (5.9 MJ/kg) body contents, leptin concentration at 16 weeks of age (2.48 ng/ml; P<0.001) and fertility (P<0.02) at first AI. Daily feed intake during pregnancy and lactation, as well as prolificacy and litter weight, were similar among groups. The highest percentage of body fat was observed for all the does when were inseminated for the first time (135 g/kg; P<0.001), consistent with the highest leptin (4.48 ng/ml; P<0.001) and total protein serum levels (6.87 g/dl; P<0.001) at this time. Serum NEFA level around parturition was higher (P<0.05) in groups AL-C and R-C (1.11 and 0.85 mmol/l) than in group AL-F (0.71 mmol/l), suggesting a lower lipid mobilization that tended to improve fertility rate for AL-F does on day 11 post-parturition (P<0.09). In conclusion, feed restriction during the rearing period delays reproductive development in young rabbits. In nulliparous does, ad libitum feeding during rearing with a high-fibre diet allows a similar productive performance to that of feeding with a less fibrous diet. Nevertheless, the use of high fibre diets during rearing does not affect feed intake throughout the first pregnancy and lactation.     

Impact of feed restriction on the performance of highly prolific lactating sows and its effect on the subsequent lactation

A total of 50 mixed parity sows of a high-prolificacy genetic line were used to evaluate the impact of feed restriction during lactation on their production and reproductive performance and their performance in the subsequent lactation. From day 7 of lactation, sows were distributed according to a completely randomized experimental design into two treatments. In treatment 1, sows were fed 8.0 kg feed/day (control) and in treatment 2, sows were fed 4.0 kg/day. The same suckling pressure was maintained until weaning on day 28 of lactation. Average minimum and maximum temperatures measured during the experimental period were 32.1°C and 16.5°C, respectively. Control sows presented significantly higher feed intake (P<0.001) compared with the restricted sows (6.43 v. 4.14 kg/day, respectively). Treatments influenced BW and backfat thickness losses (P<0.001). Control sows lost less BW than the restricted-fed sows (7.8 v. 28.2 kg). Restricted-fed sows lost more backfat thickness than those in the control group (3.97 v. 2.07 mm; P<0.01). Restricted-fed sows tended (P<0.10) to be lighter at weaning compared with the control sows (211 v. 227 kg). The composition of BW loss was influenced by the treatments (P<0.001), as the restricted-fed sows lost more body protein, lipids and energy compared with the control sows (3.90 v. 0.98 kg, 11.78 v. 4.83 kg and 584 v. 224 MJ, respectively). Litter weight gain was greater (P<0.05) in control sows than in restricted-fed sows (2.70 v. 2.43 kg/day). Daily milk production was 19% higher (P<0.01) in the control sows compared with the restricted-fed sows (8.33 v. 6.99 kg/day). However, restricted-fed sows presented a higher (P<0.05) lactation efficiency than the sows of the control group (82.30% v. 72.93%). No differences were detected (P>0.10) in weaning-to-estrus interval and averaged 4.3 days. No effect of the treatment (P>0.10) was observed on any of the studied performance traits in the subsequent lactation, except for litter size at birth that tended (15.2 v. 14.1; P<0.10) to be lower for the restricted sows. In conclusion, the present study demonstrated that feed restriction during lactation leads to intense catabolism of the body tissues of sows, negatively affecting their milk production, and the litter weight gain and possibly number of piglets born in the next litter. On the other hand, restricted-fed sows are more efficient, producing more milk per amount of feed intake.     

Evaluation of the effects of pharmacological zinc oxide and phosphorus source on weaned piglet growth performance,plasma minerals and mineral digestibility

Crossbred pigs (n=720; average age=28±3 days and weight=9.5±0.3 kg) were used in a 20-day trial in order to determine the influence of phosphorus (P) source and various doses of pharmacological zinc (Zn) on growth performance, plasma minerals and mineral digestibility. Pigs (five intact males and five females per pen) were randomly allotted to treatments in a 3×3 factorial arrangement with three sources of dietary P (4.5 g/kg digestible P, 4.5 g/kg digestible P plus 2500 phytase units (FTU)/kg, or 5.5 g/kg digestible P) and three dietary levels of supplemental Zn (0, 1750 or 3500 mg/kg) from ZnO (82% Zn) with eight pens per treatment. Diets were formulated to exceed all nutrient requirements, including calcium (Ca), P and Zn from day 0 to 20. Zn supplementation increased (quadratic P<0.05) average daily feed intake. There was a significant Zn level×P source interaction on average daily gain and feed conversion ratio (FCR). Pigs fed 4.5 g/kg digestible P without or with 2500 FTU/kg phytase gained more per day (quadratic P<0.05) and had better FCR (quadratic P<0.05) when they were fed 1750 mg/kg supplemental Zn. However, pigs fed 5.5 g/kg digestible P gained more per day (linear P<0.05) and were more efficient (linear P<0.05) when they were fed 3500 mg/kg supplemental Zn. Plasma Zn and Zn digestibility increased (linear P<0.05) as pharmacological Zn supplementation increased from 0 to 3500 mg/kg, irrespective of P source. However, Ca, P, sodium (Na), potassium (K) and copper (Cu) digestibility were reduced (P<0.05) as pharmacological Zn supplementation increased, and this was mitigated or exacerbated by the supplementation of 5.5 g/kg digestible P or phytase. In conclusion, increasing the dietary inclusion of pharmacological Zn may impact growth performance in young pigs through the interaction with minerals such as Ca, P, Na and K. Pharmacological Zn may reduce Na or K digestibility and indirectly reduce water secretion into the lumen, resulting in an increase in faecal dry matter as pharmacological Zn supplementation in the diet increased.     

Fish oil rich in eicosapentaenoic acid and docosahexaenoic acid in sow diets modifies oxylipins and immune indicators in colostrum and milk

Colostrum and milk are the first nutrient sources for newborn piglets. In addition, n-3 fatty acids (FAs) and their oxygenated derivatives (oxylipins) have the capacity to modulate immune components. The aim of the current study was to include a fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in sow diets to promote an increase of anti-inflammatory molecules in colostrum and milk to benefit piglets. Thirty-six sows were randomly assigned from insemination to the end of lactation to either a control diet with animal fat (15 g/kg in gestation and 30 g/kg in lactation) or an n-3 diet in which animal fat was totally (gestation) or half (lactation) replaced by an equivalent amount of solid fish oil. Performance of sows and piglets was monitored during the study. Colostrum and milk samples were obtained after the birth of the first piglet and at weaning, respectively. From all samples (n = 18 per treatment), FAs were quantified by gas chromatography and immunoglobulins and cytokines by ELISA. Three samples per treatment were randomly selected to analyse oxylipin composition by liquid chromatography-tandem mass spectrometry. In colostrum and in milk, the n-3 FA (P = 0.020 and P < 0.001), particularly EPA (P < 0.001 and P < 0.001) and DHA (P < 0.001 and P < 0.001), and also their oxygenated derivatives were increased in samples from sows fed n-3 diet. Fish oil had no effect on immunoglobulin concentrations, but reduced tumour necrosis factor α (TNFα) (P = 0.011) and a tendency to reduce interleukin 10 (IL10) (P = 0.059) were observed in milk. In conclusion, fish oil in sow diets increased n-3 FA, particularly EPA and DHA, and their oxygenated derivatives in colostrum and milk, reducing TNFα and IL10 in milk.     

The effect of a non-starch polysaccharide-hydrolysing enzyme (Rovabio® Excel) on feed intake and body condition of sows during lactation and on progeny growth performance

A total of 200 (Large White × Landrace) sows were used in a 39-day study to evaluate the effects of feeding a non-starch polysaccharide (NSP)-hydrolysing enzyme multicomplex (Rovabio® Excel) in conjunction with a high- or reduced nutrient-density diet during lactation on sow body condition, feed intake and progeny performance. Eight sows were selected each week for 25 weeks, blocked by parity and BW into groups of four, and within the block randomly assigned to one of the four treatments (n = 50/treatment). Treatments were: (1) LND: low energy (13.14 MJ of DE/kg), low CP (15%) diet; (2) LND + RE: LND with 50 mg/kg NSP-hydrolysing enzyme; (3) HND: high energy (14.5 MJ of DE/kg), high CP (16.5%) diet; and (4) HND + RE: HND with 50 mg/kg NSP-hydrolysing enzyme. Sows were fed treatment diets from day 109 of gestation until the day of subsequent service. Between weaning and re-service, Rovabio® Excel addition to LND diets resulted in an increase in energy intake; however, a reduction was observed when supplemented to the HND diet (P < 0.05). The inclusion of Rovabio® Excel increased feed and energy intake during week 3 (days 15 to 21) of lactation (P < 0.05). Sows fed diets supplemented with Rovabio® Excel had greater back-fat depth at weaning and service (P < 0.05); however, the magnitude of change in back-fat depth during lactation and from farrowing to service was not different between treatments. Feeding the HND diet increased energy intake before farrowing, throughout lactation and during the weaning to service interval (P < 0.01); however, overall, average daily feed intake tended to be reduced (P < 0.10). At service, sows fed the HND diet were heavier than sows fed the LND diet (P < 0.05); however, the magnitude of change in BW between treatments was not different. Feeding the HND diet to sows resulted in a tendency for heavier piglets at birth (P = 0.10) that tended to grow at a faster rate and be heavier at weaning than piglets from sows fed the LND diet (P = 0.06). These results indicate that NSP-degrading enzymes offer minimal benefit to sows and their progeny when fed before and during lactation; however, increasing energy intake of sows during lactation may beneficially affect progeny.