Adaptation capacity of Boer goats to saline drinking water

Due to global climatic changes, water and soil salinization is an increasing worldwide phenomenon, thus creating new threats for farm animal production. The present study was designed to investigate the adaptation capacity of goats towards sodium chloride (NaCl) in drinking water. Twelve non-pregnant Boer goats with an average body weight of 50.5 ± 9.0 kg were kept in individual pens. The study was conducted in four phases applying a two-choice preference test. In the control phase (phase 1) only fresh water was supplied in two containers. In phase 2, water with different salt concentrations (0.25%, 0.5%, 0.75%, 1.0%, 1.25% and 1.5%) was offered in one container and tap water in the other (sensitivity test). During the third phase (adaptation), goats were stepwise habituated to saline water by offering only saline water with different increasing concentrations (between 0% and 1.5% NaCl) in both containers. Subsequently, in phase 4 (sensitivity re-test) the same treatment as in phase 2 was repeated. Goats had ad libitum access to hay, water and a mineral licking block. Individual water and feed intake were recorded daily, while body weight and body condition score were measured every 2^nd week. Body weight was not affected by saline water intake, whereas dry matter intake and body condition scores decreased significantly during the experiment. Water intake was significantly (P<0.001) higher in phase 2 (sensitivity test) and phase 3 (adaptation), compared to phase 1 (control) and phase 4 (sensitivity re-test). Total sodium intake followed the same pattern. In phase 2, when goats had the choice between fresh and saline water for the first time they preferred higher salt concentrations and consumed significantly (P<0.001) higher amounts of saline water (75.4 ± 53.2 g/kg BW^0.82 per day) than in the re-test (40.4 ± 34.0 g/kg BW^0.82 per day) after the habituation period. Thus, salt discrimination rejection thresholds were lowered to 1.25% in phase 4 compared to 1.5% in phase 2. The results suggest that a stepwise adaptation to saline drinking water in goats is an effective method to habituate the animals to saline water intake when concentrations were below 1.5%. Goats reacted more sensitively to the salinity of drinking water after prolonged exposure to saline water indicating flexible regulation mechanisms depending on the total sodium balance of the animal.     

Efficiency of energy use for maintenance and gain by growing crossbred Boer and Spanish Goats consuming diets differing in forage level

Eight Boer (75%) × Spanish (BS) and eight Spanish (S) wether goats (155 ± 8 days of age and 19.2 ± 2.3 kg BW, initial) were used in a replicated crossover design experiment with a 2 × 2 factorial arrangement of treatments to determine the effects of genotype and diet quality on heat production with ad libitum, near maintenance and fasting levels of feed intake. Diets were 65% concentrate (CON 15% CP, DM basis) and coarsely ground alfalfa hay (FOR 23% CP). There were no significant interactions between genotype and diet. ME intake was similar between genotypes and greater (P < 0.05) for CON versus FOR both when intake was ad libitum (7.60 versus 5.43 MJ/day) and near maintenance (4.31 versus 4.09 MJ/day). DE concentration was greater (P < 0.05) for CON than for FOR with ad libitum (74.4 versus 55.5%) and restricted intake (77.0 versus 59.6%). Energy expenditure (EE), determined by respiration calorimetry, at all levels of intake was similar between genotypes. EE was greater (P < 0.05) for CON than for FOR at each of the three levels of intake, ad libitum (573 and 521 kJ/kg BW^0.75 while fasting), near maintenance (426 and 400 kJ/kg BW^0.75) and fasting (280 and 255 kJ/kg BW^0.75). Efficiencies of ME utilization for maintenance (k_m) and gain (k_g) and the ME requirement for maintenance (ME_m) were similar between genotypes. k_m was similar between diets (0.705 and 0.690 for CON and FOR, respectively), although k_g was greater (P < 0.05) for CON than for FOR (0.603 versus 0.387). ME_m was numerically greater (P < 0.17) for CON than for FOR (407 versus 379 kJ/kg BW^0.75), which may have involved higher ME intake with CON. In conclusion, under the conditions of this experiment energy requirements and efficiency of utilization were not different between growing Boer crossbred and Spanish goats regardless of diet quality.     

Comparative studies on dry matter intake,digestibility and nitrogen metabolism between Thai native (TN) and Anglo Nubian × TN bucks

Metabolic experiments were conducted for each Thai native (TN) and Anglo Nubian–TN 50% (AN × TN) bucks, 26.5–38 kg BW and 35–52 months of age, by assigning the following concentrate diets, which had four levels of CP concentrations, T1: 14%, T2: 21%, T3: 28% and T4: 35%, on a DM basis. The animals were fed the concentrates at a rate of 1% of their BW and had ad libitum access to Paspalum plicatulum hay. As the CP level increased, digestibility of CP, N excretion in urine and N retention increased (P < 0.01). No significant differences of DM digestibility among the CP levels of diet and between the breeds of bucks were observed. The AN × TN had higher DM intake than TN (P < 0.05, 40.9 g/(kg BW^0.75 day) versus 36.0 g/(kg BW^0.75 day)), thus N intake of AN × TN was higher than that of TN (P < 0.01, 0.99 g/(kg BW^0.75 day) versus 0.90 g/(kg BW^0.75 day)). Digestibility of CP and blood urea N concentrations of TN were higher than those of AN × TN (P < 0.05, 69.8% versus 64.0% and 32.2 mg/dl versus 26.7 mg/dl, respectively). The AN × TN tended to retain more N than TN in the higher CP feeding condition of T3 (0.19 g/(kg BW^0.75 day) versus 0.11 g/(kg BW^0.75 day)) and T4 (0.25 g/(kg BW^0.75 day) versus 0.17 g/(kg BW^0.75 day)). Digestibility of NDF and ADF, and TDN of TN were higher than those of AN × TN (P < 0.05, 61.1% versus 55.9%, 49.6% versus 43.5% and 65.8% versus 62.4%, respectively). The overall mean DE was 109 kcal/(kg BW^0.75 day), and no significant difference of DE among CP levels nor breeds of bucks was observed. Thai native was superior to AN × TN in digestibility of N and fiber fractions at the maintenance level of DE, which might have overcome inferiority of TN to AN × TN in amount of N and energy intake caused by the lower DMI. It is likely that TN goats are well adapted to fodder shortage condition due to their efficient utilization of nutrients.     

Seasonal changes in composition and intake of chaparral by Spanish goats

Seasonal changes in utilization of one-year regrowth of chaparral vegetation by Spanish goats were investigated. The dominant shrub species were: oak (Quercus dumosa and Q. wislizenii), chamise (Adenostoma fasciculatum), manzanita (Arctostaphylos glandulosa) and ceanothus (Ceanothus cuneatus, and C. foliosus). Oesophageal and faecal samples were obtained during the spring, summer and autumn seasons of 1979. Mean daily temperatures for the three seasons were 19, 18 and 12° C, respectively. Winter sampling was restricted by cold weather at the 985-m elevation site. Cover was measured from ten permanent transects. Preference of Spanish goats was highly directed towards oak (> 50%) and chamise (> 30%) in all seasons.Correlation of selectivity (percentage botanical composition in the diet) and availability data indicated that goats may be generalist in their feeding strategies, but display some sort of specialized behaviour in selecting between the most dominant species. The observation that selection of herbaceous vegetation was restricted by availability conforms with the recent classification of goats as adaptive mixed feeders rather than browsers.Daily feed intake (g DM/kg BW^0.75) was calculated by dividing faecal residue by (100—digestibility in vitro). Intake values were equivalent to maintenance requirements during spring (60 g) and summer (57 g). However, autumn chaparral provided sub-maintenance intake levels (36 g). Condensed tannins (ADF—NAD), estimated as the difference between acid detergent fibre (ADF) and sequential acid detergent residue of neutral detergent residue (NAD), were variable in the clipped shrub samples but low in all dietary samples (2.1 ± 1.8%). The low levels of tannins did not appear to be affecting utilization of this browse.Predictive equations for intake (DMI) and digestibility in vitro (IVOMD) were derived from step-wise regression analysis using the following independent variables: cell wall content (CWC), NAD, cellulose (NADC), NAD sulphuric acid insoluble lignin (NADL_s), hemicellulose (NADHC), lignin: ADF—NAD tannins, ash and nitrogen (N) The equation for intake was: DMI (g DM/kg BW^0.75) = ?25.67 + 1.80 OMD (n = 56, Syx = 17.72, r = 0.59, P < 0.005), while digestibility (%) was predicted as OMD = 56.98 ? 0.46 CWC ? 0.45 NADL_s + 0.65 N + 0.09 DMI (n = 56, Syx = 2.77, r = 0.88, P < 0.005).It is concluded that recently-burnt chaparral vegetation would provide a maintenance browse for Spanish goats during the spring and summer seasons only.     

Identifying the limitations for growth in low performing piglets from birth until 10 weeks of age

The evolution of hyper-prolific pig breeds has led to a higher within-litter variation in birth weight and in BW gain during the nursery phase. Based on an algorithm developed in previous research, two populations from a pool of 368 clinically healthy piglets at 6 weeks of age were selected: a low (LP) and a high (HP) performing population and their development was monitored until the end of the nursery phase (10 weeks of age). To understand the cause of the variation in growth between these populations we characterized the LP and HP piglets in terms of body morphology, behaviour, voluntary feed intake, BW gain, and apparent total tract and ileal nutrient digestibility. Piglets were housed individually and were fed a highly digestible diet. At selection, 6 weeks of age, the BW of LP and HP piglets were 6.8±0.1 and 12.2±0.1 kg, respectively. Compared with the LP piglets the HP piglets grew faster (203 g/day), ate more (275 g/day) from 6 to 10 weeks of age and were heavier at 10 weeks (30.0 v. 18.8 kg, all P<0.01). Yet, the differences in average daily gain and average daily feed intake disappeared when compared per kg BW^0.75. Assuming similar maintenance requirements per kg BW^0.75 the efficiency of feed utilization above maintenance was 0.1 g/g lower for the LP piglets (P=0.09).The gain : feed ratio was similar for both groups. LP piglets tended to take more time to touch a novel object (P=0.10), and spent more time eating (P<0.05). At 10 weeks, LP piglets had a higher body length and head circumference relative to BW (P<0.01). Relative to BW, LP had a 21% higher small intestine weight; 36% longer length, and relative to average FI, the small intestinal weight was 4 g/kg higher (both P=<0.01). Apparent total tract and ileal dry matter, N and gross energy digestibility were similar between groups (P>0.10). We concluded that the low performance of the LP piglets was due to their inability to engage compensatory gain or compensatory feed intake as efficiency of nutrient utilization and feed intake per kg BW^0.75 was unaffected. LP piglets tend to be more fearful towards novel objects. The morphological comparisons, increased body length and head circumference relative to BW imply that LP piglets have an increased priority for skeletal growth.     

Deuterium oxide dilution accurately predicts water intake in sheep and goats

The aim of this study was to test whether the deuterium oxide dilution technique accurately predicts water intake in sheep and goats. Two other issues were also studied: (i) a comparison of water intake in sheep and goats and (ii) an assessment of whether observations of drinking behaviour can accurately measure the water intake. In this study, eight dry Boer goats and eight dry German Black Head Mutton ewes were kept under controlled stable conditions. Animals had access to hay and water ad libitum. Diurnal drinking behaviour was recorded by video. Individual daily water intake was measured and estimated for 2 weeks by re-weighing water buckets and from water kinetics using the deuterium oxide dilution technique, respectively. In addition, dry matter intakes were directly measured and were significantly higher in sheep than in goats. The average daily water consumption by drinking differed significantly between the two species, with higher intakes in sheep than in goats. Total body water expressed as a percentage of body mass did not differ between species. Measurement methods of total water intake (TWI) using deuterium oxide dilution and re-weighing water buckets did not differ significantly in both species (P = 0.926). Results obtained for measured and estimated TWI confirm that the isotope dilution technique gives reliable results for estimates of water intake in sheep and goats. The higher amount of water intake in sheep was also reflected by their drinking behaviour. Sheep spent approximately 0.3% per 24-h drinking, while Boer goats spent only 0.1%. However, measured and estimated TWIs were only moderately correlated to the daily time spent drinking. The lower water intake found in Boer goats confirms a superior water management capacity compared with Black Head Mutton sheep even under temperate conditions.     

Response of growing ruminants to diet in warm climates: a meta-analysis

The aim of this work was to establish the response of growing sheep, goats and cattle to different nutritional environments. Data from 590 publications representing 2225 treatments were analysed. The results showed that each 10% increase in NDF was accompanied by 0.11 g/kg live weight (LW) and 0.32 g/kg metabolic live weight (LW^0.75) decreases in DMI. Otherwise, the response of DMI to CP (CP%DM) content was curvilinear (P<0.01), without any significant difference in the slope between species. The percentage of concentrate (% CC) affected DMI curvilinearly, without any significant difference between species. This meta-analysis demonstrated the negative linear effect of NDF and the quadratic effect of CP concentration on organic matter digestibility (OMd). For growth performance, the three species responded curvilinearly to variations in metabolisable energy intake (MEI MJ/kg LW^0.75) and digestible CP (DCPI g/kg LW^0.75) intake (P<0.01). At the same level of MEI, average daily gain (ADG) varied with CP contents of the diet, and only the intercept differences were significant between the three levels (P=0.07). At the same level of DCPI, ADG varied with energy level (below maintenance (LE−−), 1 to 1.2×maintenance (LE−), 1.2 to 1.4× maintenance (ME+−), and >1.4, corresponding to maximum growth (HE+)). No significant difference was observed between LE−− and LE−, and no significant difference was observed between ME+− and HE+. For nitrogen balance, no difference was observed between species for a given level of nitrogen intake.     

Murciano-Granadina Goat Performance and Methane Emission after Replacing Barley Grain with Fibrous By-Products

The aim of this experiment was to study the effects of substituting dietary barley grain with orange pulp or soybean hulls on energy, nitrogen and carbon balance, methane emission and milk performance in dairy goats. Twelve Murciano-Granadina dairy goats in midlactation were selected and divided into three groups based on similar body weight (42.1 ± 1.2 kg) and milk yield (2.16 ± 0.060 kg/goat/day). The experiment was conducted in an incomplete crossover design where one group of four goats was fed a mixed ration of barley grain (BRL), another group of four goats replaced barley grain with orange pulp (OP) and the last group of four goats with soybean hulls (SH). After adaptation to diets, the goats were allocated to individual metabolism cages and intake, faeces, urine and milk were recorded and analysed. Then, gas exchange measurements were recorded by a mobile open-circuit indirect calorimetry system using a head box. Dry matter intake was similar for all three groups (2.03 kg/d, on average). No influence of the diet was observed for energy balance and the efficiency of use of metabolizable energy for milk production was 0.61. The OP and SH diets showed greater (P < 0.05) fat mobilization (-42.8 kJ/kg of BW^0.75, on average) than BRL (19.2 kJ/kg of BW^0.75). Pentadecanoic acid (15:0) and heptadecanoic acid (17:0) were potential biomarkers of rumen function because the higher contents found in the milk of OP and SH goats than BRL suggest a negative impact of these diets on rumen bacterial metabolism; probably linked to the lower nitrogen supply of diet OP to synthesize microbial protein and greater content of fat in diet SH. Replacement of cereal grain with fibrous by-products did not increased enteric methane emissions (54.7 L/goat per day, on average). Therefore, lactating goats could utilize dry orange pulp and soybean hulls diets with no detrimental effect on milk performance.     

Nitrogen utilisation,energy utilisation and methane emissions of sheep grazing in two types of pasture

Livestock grazing plays a significant role in maintaining grasslands and promoting animal production globally. To understand the livestock performance in sown pasture (SP) vs native pasture (NP) is important to ensure more effective grassland-livestock interactions with minimal environmental impact. A 2 (treatment) * 2 (period) Latin Square design experiment was conducted with 10 growing Hu sheep ♂ × thin-tailed Han sheep ♀ rams grazed perennially SP vs NP in an inland arid region of China. The objectives were to evaluate the effects of grazing management on nutrient digestibility, nitrogen (N) and energy utilisation and methane (CH₄) emission. The N intake, N retained and energy intake (gross energy (GE), and digestible and metabolisable energy) of sheep grazing in SP were significantly increased compared with those grazing in NP. There were significant linear relationships between DM intake (DMI) (g/kg BW or g/kg BW^0.75) or CH₄ (g/kg BW or g/kg BW^0.75) emissions and forage nutrient and GE concentrations within each grassland type. The linear regression analysis indicated that forage CP or ether extract concentration was a good predictor for DMI (g/kg BW or g/kg BW^0.75) (R² = 0.756 or 0.752), and CH₄ emission could be predicted using forage nutrient and GE concentrations (R² = 0.381–0.503). These results suggest that DMI and CH₄ emissions per unit metabolic BW were accurately predicted by multiple-factor combinations of forage nutrients, including ether extract and CP paired with GE. The present output could provide useful information for the development of sustainable sheep grazing systems in the inland arid regions of the world.     

Water requirements of beef production can be reduced by genetic selection

Growing concerns regarding sustainability in agriculture include the availability of drinking water, which is putting pressure on livestock production, especially the beef sector, for more efficient practices. Thus, genetic parameters were estimated for traits related to water intake and water use efficiency in Senepol cattle. Senepol females (n = 925) and males (n = 191) were evaluated in performance tests carried out from 2014 to 2019. Daily dry matter intake (DMI) and water intake (WI) were recorded by electronic feed and water bunks (Intergado Ltd.). Other traits assessed included average daily gain (ADG); mid-test metabolic BW (BW^0.75); residual water intake based on ADG (RWI_ADG), estimated as the residual of the linear regression equation of WI on ADG and BW^0.75; residual water intake based on DMI (RWI_DMI), estimated as the residual of the linear regression equation of WI on DMI and BW^0.75 (RWI_DMI); water conversion ratio (= WI/ADG); gross water efficiency (GWE = ADG/WI); residual feed intake estimated as the residual of the linear regression equation of DMI on ADG and BW^0.75 (RFI); feed conversion ratio (= DMI/ADG) and gross feed efficiency. Genetic (co)variances were estimated with bivariate analyses. The heritabilities for WI, RWI_ADG and RWI_DMI were 0.38, 0.36 and 0.33, respectively. Water conversion ratio, RWI_ADG and RWI_DMI showed positive genetic and phenotypic correlations with WI, whereas GWE was negatively correlated with WI, suggesting that traits related to water use efficiency may be useful to identify cattle with reduced WI. Water intake showed positive genetic (r = 0.79) and phenotypic (r = 0.60) correlations with DMI, suggesting the use of WI to estimate DMI in future studies. Both RWI_ADG and RWI_DMI were genetically correlated with RFI (0.67 and 0.57, respectively) and ADG (0.49 and 0.44, respectively), showing that RWI is positively associated with feed efficiency, but has an antagonistic relationship with growth. This antagonism, however, may be managed using selection indexes. Genetic improvement of water use efficiency in Senepol cattle is possible through selection and may reduce the water requirements of beef production systems.     

The feeding height preferences of two goat breeds fed Grewia occidentalis L. (Tiliaceae) in the Eastern Cape,South Africa

Nguni goats and Boer goats, which are farmed together in the savannas of the Eastern Cape Province, depend on the same feed resources. The feeding height intake rates and preferences of one of their most preferred browse species, Grewia occidentalis L. (Tiliaceae), were studied in order to indirectly determine resource partitioning between these goat breeds on the basis of feeding height. The two hypotheses tested were that taller Boer goats feed at higher levels than do Nguni goats and that both breeds have feeding height preferences that are related to differences in intake rates. Four individuals of each breed were fed branches attached to a height foraging board. The two breeds showed no particular height preference in either season. Bite rates varied with feeding height, while bite sizes and intake rates increased with feeding height. Boer goats had lower bite rates compared to Nguni goats, although both breeds achieved similar bite sizes and intake rates. Bites sizes and intake rates for both breeds were higher in summer than in winter, possibly because more browse biomass was available per branch in summer than in winter since G. occidentalis is deciduous. There was no evidence to support that feeding height preference was related to differences in intake rates. It is concluded that Boer goats may compete for forage resources during times of resource limitation. Thus, Nguni goats might be a more favourable breed in semi-arid savannas because of their smaller body-size and, therefore, absolute nutrient requirements as well as their better reproductive performance compared to Boer goats.     

Arterial hypotension in ducks adapted to high salt intake

Summary A homogeneous group of 8-week-old Pekin ducks was divided into two groups: saltwater (SW) ducks received salt water of gradually increasing salinity (200–600 mOsm·kg^-1) from the 8th to 20th week of age; freshwater (FW) ducks were maintained on fresh water but otherwise treated identically. During the course of salt-adaptation SW ducks increased plasma osmolality, Na⁺ and Cl^- levels, and concentrations of the osmoregulatory peptide hormones arginine vasotocin and angiotensin II. The apparent volume of inulin distribution decreased in SW ducks, but blood volume was not reduced. SW ducks also developed arterial hypotension, bradycardia, and reduced cardiac output in the course of salt adaptation. This depressed cardiovascular performance was associated with enhanced vagal restraint of cardiac function and reduced plasma concentrations of norepinephrine. Salt water adaptation did not alter the degrees to which mean arterial pressure and heart rate changed in response to intravenous bolus injections of catecholamines. The same applied to the osmoregulatory peptides which were, however, effective only at supraphysiological concentrations. The Pekin duck, as a bird predisposed for adaptation to high salt loads, presumably adapts to chronic hypertonic saline intake by resetting the central autonomic control of blood pressure to a lower level.Abbreviations FW ducks fresh water ducks - SW ducks salt water ducks - ANGI angiotensin II - AVT arginine vasotocin - MAP mean arterial pressure - HR heart rate - IV intravenous - CO cardiac output - SV stroke volume - TPR total peripheral resistance - ISp virtual inulin space - ECFV extracellular fluid volume     

Evaluation of soil intake by growing Creole young bulls in common grazing systems in humid tropical conditions

Soil is the main matrix which contributes to the transfer of environmental pollutants to animals and consequently into the food chain. In the French West Indies, chlordecone, a very persistent organochlorine pesticide, has been widely used on banana growing areas and this process has resulted in a long-term pollution of the corresponding soils. Domestic outside-reared herbivores are exposed to involuntary soil intake, and tethered grazing commonly used in West Indian systems can potentially favour their exposure to chlordecone. Thus, it appears necessary to quantify to what extent grazing conditions will influence soil intake. This experiment consisted of a cross-over design with two daily herbage allowance (DHA) grazed alternatively. Six young Creole bulls were distributed into two groups (G1 and G2) according to their BW. The animals were individually tethered and grazed on a restrictive (RES) or non-restrictive (NRES) levels of DHA during two successive 10-days periods. Each bull progressed on a new circular area every day. The two contrasting levels of DHA (P<0.001) were obtained via a different daily grazing surface area (RES: 20 m²/animal, NRES: 31 m²/animal; P<0.01) offered to the animals by the modulation of the length of the tethering chain (RES: 1.9 m, NRES: 2.6 m). These differences in offered grazing areas resulted in DHA of 71 and 128 g DM/kg BW^0.75, respectively for RES and NRES treatments. As expected, the animals grazing on the reduced area realized a lower daily dry matter intake (DMI) (RES: 1.12 kg/100 kg BW, NRES: 1.83 kg/100 kg BW; P<0.05) and present a lower organic matter digestibility (RES: 0.67, NRES: 0.73; P<0.01) than NRES ones, due in part to the shorter post-grazing sward surface height (RES: 3.3 cm, NRES: 5.2 cm; P<0.01) of their grazing circles. Soil intake was estimated on an individual level based on the ratio of the marker titanium in soil, herbage and faeces. Grazing closer to the ground, animals on RES treatment ingested a significantly higher proportion of soil in their total DMI (RES: 9.3%, NRES: 4.4%; P<0.01). The amount of ingested soil in the diet was not significantly different between the two treatments (RES: 98 g/100 kg BW, NRES: 78 g/100 kg BW; P>0.05) due to the lower DMI of RES compared with NRES treatment.     

Determination of maintenance energy requirement and responses of dry ewes to dietary inclusion of lucerne versus concentrate meal

An accurate value for metabolizable energy (ME) requirement for maintenance (ME_m) is essential to enable sheep husbandry practice to reach its potential. The objectives of the study were to use calorimetry chamber data of dry ewes (Hu × thin-tail Han F1 crossbred) to develop updated ME_m, examine effects of substituting concentrate feed with lucerne hay on energy partitioning, and explore the relationships between energy utilization and fasting heat production (FHP). Data were collected from three experiments. In Exps. 1, 2a and 2b, lucerne hay was used to replace concentrates in three levels (0:40%, 15:25% and 30:10%), with diets containing 60% maize stover (Exp. 1), fresh rye forage (Exp. 2a) or dry rye forage (Exp. 2b). Within each experiment, diets were isoenergetic (digestible energy, DE) and isonitrogenous. Exp. 3 aimed at evaluating effects of three BW levels on nutrient utilization of dry ewes offered diets containing 60% maize stover, 15% lucerne hay and 25% concentrates. Energy metabolism data were measured using the respiration calorimeter chamber technique in all three experiments, followed by the measurement of FHP in Exps. 1, 2b and 3. The ME_m derived from the linear regression between energy balance (EB) and ME intake was 0.440 MJ/kg BW^0.75. The average FHP was 0.326 MJ/kg BW^0.75. The fasting metabolism, net energy requirement for maintenance (NE_m) and ME_m were estimated to be 0.336, 0.359 and 0.511 MJ/kg BW^0.75, respectively, through adjustment of FHP using fasting urinary energy output, activity allowance and efficiency of ME use for maintenance. The FHP was negatively correlated to EB/metabolic BW, ME/gross energy (GE), ME/DE, EB/GE intake and EB/ME intake, while positively correlated to HP/GE intake, HP/ME intake and CH₄-E/GE intake. Compared to zero lucerne hay diet, the 15% lucerne hay intake decreased HP (MJ/d), and had no negative effects on EB (MJ/d) or energy utilization efficiencies. The results indicate that nutrient requirement standards currently used across the world are likely to underestimate ME_m for dry ewes, and the selection of low FHP ewes for breeding has the potential to improve sheep production efficiency.     

Sow and piglet factors determining variation of colostrum intake between and within litters

Colostrum intake has a short- and long-term beneficial impact on piglet performance and mortality. Sows’ colostrum production and piglets’ colostrum intake are limited and highly variable. The present study investigated sow and piglet factors explaining the variation of colostrum intake between and within litters. The CV for colostrum intake and birth weight (BW_b) of all piglets within a litter was calculated to evaluate the variation of colostrum intake and BW_b within a litter (colostrum and litter BW_b heterogeneity, respectively). A total of 1937 live-born piglets from 135 litters from 10 commercial herds were included. Colostrum intake per piglet averaged 371±144 g and was affected by breed (P=0.02). It was lower when oxytocin was administered to the sow during parturition (P=0.001) and with increased litter size (P<0.001). It was higher when the interval between birth and first suckling decreased (t_FS, P<0.001). Colostrum intake was positively influenced by BW_b (P<0.001) and this association was more pronounced in piglets from Topigs (P=0.03) and Hypor (P=0.03) sows compared with piglets from Danbred sow breeds. The positive relationship between colostrum intake and BW_b was more pronounced when t_FS lasted longer (P=0.009). Heterogeneity in colostrum intake averaged 31±11%, it increased when oxytocin was applied during farrowing (P=0.004) and when stillbirth occurred (P=0.006). Colostrum heterogeneity was positively associated with litter size (P<0.001) and litter BW_b heterogeneity (P=0.01). The positive relationship between colostrum and litter BW_b heterogeneity was more pronounced when oxytocin was applied during farrowing (P=0.04). The present study demonstrated that oxytocin should be used cautiously in sows during farrowing. Farrowing and colostrum management should prevent or counteract the adverse influences of stillbirth, large and heterogeneous litters on colostrum intake and colostrum heterogeneity. The study also confirmed the expected association between BW_b and colostrum intake and indicated that the impact of BW_b on colostrum intake was different among breeds (Hypor v. Danbred) and dependent on piglets’ latency to first suckling. Hence, colostrum management should focus on low birth weight piglets, especially in some breeds, and low colostrum intake in low birth weight piglets can be counteracted by shortening the t_FS.     

Histidine maintenance requirement and efficiency of its utilization in young pigs

Abstract

An experiment was conducted in young pigs (initial BW 10.1 kg) to estimate the maintenance requirement for histidine and its efficiency of utilization for protein accretion using a comparative slaughter technique. Three groups of six pigs each were fed a purified diet supplying 0, 14 or 56 mg histidine per kg BW^0.75. Following 21 d of feeding, pigs were killed for whole body compositional analysis. A representative group of six pigs was killed at the beginning of the experiment. Retention of histidine and total N were the main criteria of response. Histidine retention (R² = 0.73) and N retention (R² = 0.78) were linear functions of histidine intake (p < 0.001). Histidine requirement for zero histidine retention was 15.5 mg/kg BW^0.75, whereas histidine required for zero N retention was 4.1 mg/kg BW^0.75. At zero histidine retention, the pigs retained daily 82 mg N/kg BW^0.75, presumably due to the degradation of histidine-rich compounds such as haemoglobin and/or carnosine. The slope of the regression line relating histidine retention to N retention indicated that 105 mg of histidine was deposited per gram of total N which was considerably less than the estimated histidine concentration in body protein (179 mg/g N). Based on the slopes of regression equations for histidine and N retention, marginal efficiency of histidine utilization was calculated to be 0.94 and 1.34, respectively.     

Effect of high dietary fat content on heat production and lipid and protein deposition in growing immunocastrated male pigs

In immunocastrated (IC) pigs, revaccination (V2) increases lipid deposition (LD) because of increased voluntary feed intake; but little is known on associated effect of diet composition on partitioning of nutrients in IC pigs. Digestibility measurements, N and energy balances in respiration chambers were performed in two subsequent stages in four replicates of two male littermates to determine the changes between 85 (stage 1) and 135 (stage 2) kg live weight due to combined effect of IC, growth and increased feed intake (IC/growth). During stage 1, pigs received a standard low-fat diet (LF diet; 2.5% dry matter (DM) of fat fed at 2.27 MJ metabolizable energy (ME)/kg BW^0.60 per day), whereas during stage 2, feed intake was increased to 2.47 MJ ME/kg BW^0.60 per day and one littermate was fed LF diet whereas the second received a fat-enriched diet (HF diet; 8.9% DM of fat) to determine the effect of increased dietary fat content on energy utilization in IC pigs. Results from N balance and measurements of gas exchanges were used to calculate respiratory quotient (RQ), heat production (HP), nutrient contribution to fat retention, components of HP, protein deposition (PD) and LD. Nutrients and energy apparent digestibility coefficients, methane losses and N retention (P<0.05) increased with IC/growth. Despite higher ME intake, total HP remained similar (1365 kJ/kg of BW^0.60 per day; P=0.47) with IC/growth. Consequently, total retained energy (RE) increased with IC/growth (from 916 to 1078 kJ/kg of BW^0.60 per day; P<0.01) with a higher fat retention (625 to 807 kJ/kg BW^0.60 per day; P<0.01), originating mainly from carbohydrates associated with a higher lipogenesis (536 to 746 kJ/kg BW^0.60 per day; P<0.01) and RQ (1.095 to 1.145; P<0.01). Both PD (from 178 to 217 g/day; P=0.02) and LD (from 227 to 384 g/day; P<0.01) increased due to IC/growth. Feeding HF diet after IC was associated with increased crude fat digestibility (P<0.01) and increased RE as fat (807 to 914 kJ/kg BW^0.60 per day; P=0.03), originating mainly from dietary fat (P<0.01) and resulting in increased LD (384 to 435 g/day; P<0.01) and lower RQ (from 1.145 to 1.073; P<0.01). Altogether, present results indicate that increased fatness of IC pigs is a result of increased daily LD caused by higher energy intake and lower basal metabolic rate. In addition, LD is further enhanced by dietary energy enrichment with fat after V2.     

Updating maintenance energy requirement for the current sheep flocks and the associated effect of nutritional and animal factors

There is evidence indicating that using the current UK energy feeding system to ration the present sheep flocks may underestimate their nutrient requirements. The objective of the present study was to address this issue by developing updated maintenance energy requirements for the current sheep flocks and evaluating if these requirements were influenced by a range of dietary and animal factors. Data (n = 131) used were collated from five experiments with sheep (5 to 18 months old and 29.0 to 69.8 kg BW) undertaken at the Agri-Food and Biosciences Institute of the UK from 2013 to 2017. The trials were designed to evaluate the effects of dietary type, genotype, physiological stage and sex on nutrient utilization and energetic efficiencies. Energy intake and output data were measured in individual calorimeter chambers. Energy balance (E_g) was calculated as the difference between gross energy intake and a sum of fecal energy, urine energy, methane energy and heat production. Data were analysed using the restricted maximum likelihood analysis to develop the linear relationship between E_g or heat production and metabolizable energy (ME) intake, with the effects of a range of dietary and animal factors removed. The net energy (NE_m) and ME (ME_m) requirements for maintenance derived from the linear relationship between E_g and ME intake were 0.358 and 0.486 MJ/kg BW^0.75, respectively, which are 40% to 53% higher than those recommended in energy feeding systems currently used to ration sheep in the USA and the UK. Further analysis of the current dataset revealed that concentrate supplement, sire type or physiological stage had no significant effect on the derived NE_m values. However, female lambs had a significantly higher NE_m (0.352 v. 0.306 or 0.288 MJ/kg BW^0.75) or ME_m (0.507 v. 0.441 or 0.415 MJ/kg BW^0.75) than those for male or castrated lambs. The present results indicate that using present energy feeding systems in the UK developed over 40 years ago to ration the current sheep flocks could underestimate maintenance energy requirements. There is an urgent need to update these systems to reflect the higher metabolic rates of the current sheep flocks.     

The development of a model to predict BW gain of growing cattle fed grass silage-based diets

The objective of this meta-analysis was to develop and validate empirical equations predicting BW gain (BWG) and carcass traits of growing cattle from intake and diet composition variables. The modelling was based on treatment mean data from feeding trials in growing cattle, in which the nutrient supply was manipulated by wide ranges of forage and concentrate factors. The final dataset comprised 527 diets in 116 studies. The diets were mainly based on grass silage or grass silage partly or completely replaced by whole-crop silages, hay or straw. The concentrate feeds consisted of cereal grains, fibrous by-products and protein supplements. Mixed model regression analysis with a random study effect was used to develop prediction equations for BWG and carcass traits. The best-fit models included linear and quadratic effects of metabolisable energy (ME) intake per metabolic BW (BW^0.75), linear effects of BW^0.75, and dietary concentrations of NDF, fat and feed metabolisable protein (MP) as significant variables. Although diet variables had significant effects on BWG, their contribution to improve the model predictions compared with ME intake models was small. Feed MP rather than total MP was included in the final model, since it is less correlated to dietary ME concentration than total MP. None of the quadratic terms of feed variables was significant (P>0.10) when included in the final models. Further, additional feed variables (e.g. silage fermentation products, forage digestibility) did not have significant effects on BWG. For carcass traits, increased ME intake (ME/BW^0.75) improved both dressing proportion (P<0.01) and carcass conformation (P<0.001) and increased (P<0.001) carcass fat score. Increased dietary CP concentration had no significant (P>0.10) effect on dressing proportion or carcass conformation score, but it increased (P<0.01) carcass fat score. The current study demonstrated that ME intake per BW^0.75 was clearly the most important variable explaining the BWG response in growing cattle. The effect of increased ME supply displayed diminishing responses that could be associated with increased energy concentration of BWG, reduced diet metabolisability (proportion of ME of gross energy) and/or decreased efficiency of ME utilisation for growth with increased intake. Negative effects of increased dietary NDF concentration on BWG were smaller compared to responses that energy evaluation systems predict for energy retention. The present results showed only marginal effects of protein supply on BWG in growing cattle.     

Methane emissions from two breeds of beef cows offered diets containing barley straw with either grass silage or brewers’ grains

Increasing the concentration of dietary lipid is a promising strategy for reducing methane (CH₄) emissions from ruminants. This study investigated the effect of replacing grass silage with brewers’ grains on CH₄ emissions of pregnant, non-lactating beef cows of two breeds. The experiment was a two×two factorial design comprising two breeds (LIMx, crossbred Limousin; and LUI, purebred Luing) and two diets consisting of (g/kg diet dry matter (DM)) barley straw (687) and grass silage (301, GS), or barley straw (763) and brewers’ grains (226, BG), which were offered ad libitum. Replacing GS with BG increased the acid-hydrolysed ether extract concentration from 21 to 37 g/kg diet DM. Cows (n=48) were group-housed in equal numbers of each breed across two pens and each diet was allocated to one pen. Before measurements of CH₄, individual dry matter intake (DMI), weekly BW and weekly body condition score were measured for a minimum of 3 weeks, following a 4-week period to acclimatise to the diets. CH₄ emissions were subsequently measured on one occasion from each cow using individual respiration chambers. Due to occasional equipment failures, CH₄ measurements were run over 9 weeks giving 10 observations for each breed×treatment combination (total n=40). There were no differences between diets for daily DMI measured in the chambers (9.92 v. 9.86 kg/day for BG and GS, respectively; P>0.05). Cows offered the BG diet produced less daily CH₄ than GS-fed cows (131 v. 156 g/day: P<0.01). When expressed either as g/kg DMI or kJ/MJ gross energy intake (GEI), BG-fed cows produced less CH₄ than GS-fed cows (13.5 v. 16.4 g/kg DMI, P<0.05; 39.2 v. 48.6 kJ/MJ GEI, P<0.01). Breed did not affect daily DMI or CH₄ expressed as g/day, g/kg DMI or kJ/MJ GEI (P>0.05). However, when expressed as a proportion of metabolic BW (BW^0.75), LUI cows had greater DMI than LIMx cows (84.5 v. 75.7 g DMI/kg BW^0.75, P<0.05) and produced more CH₄ per kg BW^0.75 than LIMx cows (1.30 v. 1.05 g CH₄/kg BW^0.75; P<0.01). Molar proportions of acetate were higher (P<0.001) and propionate and butyrate lower (P<0.01) in rumen fluid samples from BG-fed compared with GS-fed cows. This study demonstrated that replacing GS with BG in barley straw-based diets can effectively reduce CH₄ emissions from beef cows, with no suppression of DMI.