Optimal grazing of wapiti (Cervus elaphus) on grassland: Patch and feeding station departure rules

Summary We studied factors which may shape giving-up decisions of wapiti grazing grassland patches (area where a wapiti initiates and terminates a feeding sequence) and feeding stations (area within a patch that a wapiti can reach without moving its forelegs). In grassland patches, cropping rate decreased after a critical period, whereas at feeding stations cropping rate increased with cumulative bites consumed. The number of feeding stations grazed, number of bites taken and grazing time did not dictate the termination of grazing in a patch. Wapiti gave up a patch only after the cropping rate at a feeding station dropped below the seasonal expectation during trials on lush pasture in May, but gave up after the cropping rate dropped below the seasonal expectation at two consecutive feeding stations in March/April and August when foraging conditions were less favourable. This confirmed a prediction of the marginal value theorem. Wapiti did not give up a feeding station according to bites taken, grazing time or cropping rate, but they left feeding stations when their lateral neck angle reached a critical point suggesting a biokinetic explanation. Leaving feeding stations when ungrazed forage can no longer be reached and patches when intake rate drops both appeared to be rules used by wapiti grazing grasslands of the boreal mixed wood forest.     

The effect of differences in herbage height on the grazing behaviour of lactating Bennett's wallabies (Macropus rufogriseus rufogriseus)

The grazing behaviour of lactating Bennett's wallabies was studied on a number of different pasture types. Increases in mean sward height resulted in a greatly reduced bite rate and an increase in the search time per bite. All wallabies showed a diurnal rhythm in grazing activity irrespective of habitat type, with least grazing activity at midday and most at night. Animals maintained on very short grass swards compensated for the reduced herbage mass by extending their grazing activity into the midday period. Lactating animals grazed for longer, had higher biting rates and a greater number of estimated bites per day than non-lactating wallabies (17,700 vs. 7600 bites per day, respectively). In general, the response of wallabies to changes in herbage availability is similar to domestic ruminants, although wallabies may be able to graze for longer each day than ruminants.     

Influence of level of nutrition during late pregnancy on reproductive productivity of red deer (2) Adult hinds gestating wapitixred deer crossbred calves

The present study aimed to relate feed intake of red deer hinds in the later stages of gestating wapitixred deer crossbred foetuses on dam body condition, gestation length, birth weight and calf growth. Multiparous hinds (N=18) conceiving at known dates to either wapiti (n=12) or red deer (n=6) sires were housed in individual pens from days 150-220 of pregnancy, during which time they were offered either ad libitum access to pelletised rations (n=6 crossbred-bearing hinds [HH] and n=6 red deer-bearing hinds [RH]) or a restricted offer (n=6 crossbred-bearing hinds [HL]) set at 70% of the average ad libitum intake of HH hind in the previous week. Hinds were returned to pasture at day 220 and calving was closely monitored. Liveweights, body condition score (BCS), and lactation score (LS) of hinds were recorded weekly from day 130 of pregnancy until calves were weaned at 12 weeks of age. Calves were tagged and weighed at birth, and subsequently weighed at 7 and 12 weeks of age. HH and RH hinds exhibited similar patterns and levels of MEI/kg0.75, which peaked at 7.8 MJME/kg0.75 at day 220. HL hinds peaked at approximately 5 MJME/kg0.75 and showed significantly lower rates of liveweight gain during pregnancy. Interestingly, both crossbred-bearing groups initiated mammary development in advance of the RH hinds. While there were significant effects of foetal genotype on mean gestation length (239 days versus 234 days for crossbred versus red deer) and mean birth weight (14.5 kg versus 10 kg), the nutritional contrast for gestation length of crossbred-bearing hinds (i.e. HH versus HL) was not significant but approached significance for birth weight (14.5 kg versus 11.9 kg; P=0.06). Regression analysis revealed weak relationships between changes in hind liveweight and gestation length (P>0.05) but a significant relationship with birth weight (P<0.05). However, change in hind BCS was significantly related to both gestation length and birth weight. Crossbred calves reared by HH hinds were 30% heavier at 7 and 12 weeks of age than the red deer calves. However, those reared by HL hinds were significantly lighter than their genotype contemporaries and only marginally heavier than the red deer calves. These results generally contrast with the previous studies on red deer hinds gestating red deer foetuses [Asher, G.W., Mulley, R.C., O'Neill, K.T., Scott, I.C., Jopson, N.B., Littlejohn, R. 2004. Influence of level of nutrition during late pregnancy on reproductive productivity of red deer, (1) Adult and primiparous hinds gestating red deer calves. Anim. Reprod. Sci., in press] and indicate that the genetically determined higher growth requirements of crossbred foetuses may override any mechanism of compensatory control of gestation length at the expense of calf birth weight. Furthermore, there were marked carryover effects of late gestational feeding on crossbred calf growth and their dam's BCS that highlight the high nutritional demands of lactation.     

Grazing behaviour of free-ranging donkeys and Shetland ponies in different reproductive states

We investigated how free-ranging mares of two species of equids (donkeys and Shetland ponies) modify their foraging behaviour to meet the increased nutritional requirements induced by lactation. We initially hypothesised that lactating mares would graze for a longer time and/or graze faster than non-lactating (dry) mares. The grazing behaviour of free-ranging animals, foraging in two low-productive dune areas, was recorded during 1 year. Results show that in both species lactating animals did not spend more time grazing than non-lactating mares. However, lactating animals took more bites, and therefore achieved a higher bite rate than dry mares. Several factors affected the differences between lactating and non-lactating animals. Lactating mares took more bites only in grassy and rough vegetations and they did this only in patches with a short sward height. In addition, lactating mares took more bites of grasses only and not of forbs or woody plants. We conclude that the extra grazing effort of the lactating animals was not distributed randomly. Lactating mares invested their extra grazing effort principally towards those items that are the most grazed by the equids in general. We propose some hypotheses to explain why lactating mares increase their bite rate instead of augmenting the time spent grazing.     

From feeding station to patch: scaling up food intake measurements in grazing cattle

The technique of grazing cut sods was used in combination with sound and video recording to examine the feasibility of using small-scale depletion curves derived from stall trials to estimate forage intake of cattle at the pasture. Setaria lutescens sods were grazed for a variable number of bites to generate patch depletion curves. Depletion curves characterize forage intake as a function of the number of bites taken at a single feeding station. Thus, the method agrees with a hierarchical approach to foraging and it could be used as a basis for scaling up food intake measurements to larger spatial scales. Two sod experiments were carried out, with the second experiment as a validation for predictions of intake. A field experiment was carried out to validate the predictions from the sod experiments with respect to both the amount and the rate of intake. Bite weight was largely determined by initial sward height and depletion level. Cumulative dry matter intake from the sods was well described by a rectangular hyperbola including the variables of number of bites and sward height. Bulk density added little to the explained variation, but was an important factor to account for the dry matter intake on short, dense sods from the second experiment. Feeding time could be explained to a great extent by the number of bites and chews taken, both in the sod and in the field experiments. However, the animals were substantially faster when grazing in the field than on the sods due to a relatively smaller chewing effort. The estimate of bite weight in the field based on the sod depletion curves was validated by an independent estimate derived from the chew to bite ratio. Bite weight estimates that ignored feeding station depletion were significantly greater than the independent estimates. We conclude that the sod grazing technique is an adequate tool to investigate food intake and forage depletion by grazing. It shows promise as a tool to explicitly scale up of foraging behaviour from the level of the feeding station to that of larger patches.     

Behavioural responses of cattle to shared foraging with wild herbivores in an East African rangeland

We assessed whether prior foraging by wild herbivores affected foraging behaviour of cattle in Laikipia rangeland, Kenya, during February 2001, August 2001 and February 2002. The study compared cattle bite rate, step rate and bites per step in plots exclusively accessible to cattle and those accessible to cattle and large wild herbivores. During February 2001 when conditions were dry, cattle bite rate was 18–19% lower, step rate 25–26% higher, and bites per step 36% lower in plots shared by cattle and wildlife compared to those exclusively accessible to cattle. Differences in these measured foraging behaviour parameters were strongly correlated with reductions in herbage cover in plots accessible to wild herbivores. Plot differences in herbage cover and the measured foraging behaviour parameters were not significant in the subsequent trials when conditions were wet, suggesting that wild herbivore impacts reported here are short-term within season and dependent on weather conditions (and plant productivity). With reduced herbaceous plant cover in wildlife grazed realms in the dry season, cattle respond with increased travel and reductions in bite rate and bites per step, suggesting that wild herbivores can seasonally affect foraging behaviour of cattle. It remains to be demonstrated whether or not these altered behaviours of cattle affect weight gains or other measures of performance.     

苏格兰拉姆岛上野化山羊种群的取食生态学

2000年6～11月对苏格兰拉姆岛上野化山羊(Capra hircus)种群的取食生态学进行了研究.研究表明:山羊的觅食回合长度变化范围从1min到460 min不等,平均觅食回合长度是103.1±15.0 (SD)min,雌性动物的觅食回合长度较雄性的长(P=0.077).野化山羊单位时间的取食频率平均为46.3±0.6 口/min,取食频率随性别(P=0.023)和月份(P<0.001)而显著变化.雄性山羊在繁殖交配之前(6～7月)和之后(10～11月)的取食频率比繁殖交配期中(9～10月)的快(P<0.008),但雌性动物并没有这样的变化(P=0.327).雄性动物在繁殖交配期中的取食时间显著减少.雌、雄两性动物在取食频次和取食时间方面的这些差异可能导致该山羊种群在食物摄入量上的性别差异:雌性山羊的食物摄入量相对比较稳定,而雄性山羊的摄入量则变动很大.估计的食物摄入量随月份而下降(尽管9月份以后有一微小幅度的上升),这意味着拉姆岛上的山羊种群在食物匮乏而天气寒冷潮湿的冬季可能面临着能量收支不平衡的威胁.     

Can grazing sheep compensate for a daily foraging time constraint?

1. Theoretical studies of large herbivore foraging assume that total daily grazing time is a key constraint on daily intake and diet choice. We experimentally tested this assumption and investigated the effects of food availability on the ability of grazing sheep to compensate for restriction of available daily grazing time.
2. Foraging behaviour, intake and diet digestibility by sheep, were measured on grass pastures in a replicated 2 × 2 factorial experiment, in which overnight access to pasture was varied (restricted overnight and continuous access) on two sward heights (5·5 and 3·0 cm), representing high and low food availability.
3. Regardless of food availability, the overnight-restricted sheep fed for almost all of the available grazing time by grazing for fewer, longer foraging bouts, but still had much shorter total daily grazing time than the continuous access sheep.
4. In response to overnight penning, the sheep had a significantly higher instantaneous rate of intake achieved mainly via larger bites. The continuous access sheep were hence not maximizing their short-term rate of intake, whilst grazing according to the daily schedule considered normal for sheep.
5. The behavioural responses to overnight food restriction were able to counteract the reduction in daily grazing time only where food availability was high. In contrast on short swards overnight grazing restriction led to a reduction in total daily intake. We suggest that the interactions between the factors considered as constraints on foraging behaviour of herbivores are, as yet, only poorly quantified.     

The role of foraging behaviour in the sexual segregation of the African elephant

Elephants (Loxodonta africana) exhibit pronounced sexual dimorphism, and in this study we test the prediction that the differences in body size and sociality are significant enough to drive divergent foraging strategies and ultimately sexual segregation. Body size influences the foraging behaviour of herbivores through the differential scaling coefficients of metabolism and gut size, with larger bodied individuals being able to tolerate greater quantities of low-quality, fibrous vegetation, whilst having lower mass-specific energy requirements. We test two distinct theories: the scramble competition hypothesis (SCH) and the forage selection hypothesis (FSH). Comprehensive behavioural data were collected from the Pongola Game Reserve and the Phinda Private Game Reserve in South Africa over a 2.5-year period. The data were analysed using sex as the independent variable. Adult females targeted a wider range of species, adopted a more selective foraging approach and exhibited greater bite rates as predicted by the body size hypothesis and the increased demands of reproductive investment (lactation and pregnancy). Males had longer feeding bouts, displayed significantly more destructive behaviour (31% of observations, 11% for females) and ingested greater quantities of forage during each feeding bout. The independent ranging behaviour of adult males enables them to have longer foraging bouts as they experience fewer social constraints than females. The SCH was rejected as a cause of sexual segregation due to the relative abundance of low quality forage, and the fact that feeding heights were similar for both males and females. However, we conclude that the differences in the foraging strategies of the sexes are sufficient to cause spatial segregation as postulated by the FSH. Sexual dimorphism and the associated behavioural differences have important implications for the management and conservation of elephant and other dimorphic species, with the sexes effectively acting as distinct “ecological species”.     

Restricting dairy cow access time to pasture in autumn: The effects on milk production,grazing behaviour and DM intake of late lactation dairy cows

Extending the grazing season in pasture based systems of dairy production can increase farm profitability; poor weather and soil conditions can reduce the number of grazing days. The study objectives were to (i) examine the effect of restricted access to pasture in the autumn on the milk production, grazing behaviour and DM intake (DMI) of late lactation spring-calving dairy cows and (ii) establish the effect of alternating restricted and continuous access to pasture on dairy cow production, DMI and grazing behaviour. Cows were randomly assigned to one of four grazing treatments: (i) 22 h (full-time) access to pasture (22H; control); (ii) Two 5-h periods of access to pasture (2×5H); (iii) Two 3-h periods of access to pasture (2×3H); and (iv) alternating between full-time and 3-h access to pasture with no more than three continuous days on any one regime, e.g. Monday – full-time access, Tuesday − 2x3H access, Wednesday − 2x3H access; Thursday – full-time access, etc. (2×3HV). Restricted access to pasture was offered after a.m. and p.m. milking. Swards of similar quality and pregrazing herbage mass were offered. Treatment had no effect on milk yield (13.2 kg/day), milk fat (48.2 g/kg), protein (39.0 g/kg) or lactose content (42.6 g/kg) and milk solid yield (1.15 kg/day). Similarly, there was no effect of treatment on final BW (483 kg) or final BCS (2.66). There was no significant difference in DMI (15.1 kg DM/cow/day) between treatments. There was an effect on daily grazing time, 22H cows (565 min/cow/day) grazed for longest time, however, when the 2x3HV treatment had full-time access to pasture, they had a similar grazing time (543 min/cow/day) to the 22H cows and were similar to the 2x3H treatment on days with restricted access to pasture (357 min/cow/day). The 22H and 2x5H animals had similar grass DMI/min (29.2 g/min), the 2x3HV were higher (33.9 g/min) but were similar to the comparable treatment when offered 2x3H access time (41.6 g/min) and when offered 22H access time (27.7 g/min). The results from this study show how when offered a grass only diet of autumn pasture grazing behaviour can be modified by restricting pasture access time without reducing dairy cow production in late lactation at low production levels. There was also no effect of alternating access time between 22H and 2x3H on milk production and DMI in the 2x3HV treatment. Restricted access time to pasture in autumn may be a strategy which farmers can use to extend the grazing season.     

Influence of stock density and rate and temporal patterns of forage allocation on the diet mixing behavior of sheep grazing sagebrush steppe

An animal's ability to select a diet depends on forage availability, the density of herbivores, and the allocation of forage resources. We hypothesized that the temporal and spatial availability of forages in sagebrush steppe vegetation both influence food selection and may encourage lambs to learn to use sagebrush, a shrub that contains high levels of terpenes that limit food intake. We conducted a field study with three treatments of 20 lambs each. Forage resources were manipulated by restricting grazing areas. Lambs in treatment H grazed at a high stock density, whereas lambs in treatment L grazed at a low stock density; both groups were moved to fresh pasture daily. Lambs in treatment H3 had three times the area of treatment H, but they were moved every 3 days, making the total area grazed by H and H3 equal, but with a different temporal allocation of forage. Scan sampling was used to record the incidence of consumption among sagebrush and understory herbs. During 24 days of conditioning, stock density and temporal patterns of forage allocation both influenced the behavior of lambs. Lambs in H spent more time foraging on sagebrush (25%) than lambs in H3 (16%), and lambs in both H and H3 spent more time foraging on sagebrush than lambs in L (1%) (P < 0.05). For lambs in H3, foraging on sagebrush was cyclic and depended on the daily availability of herbs. Use of sagebrush, expressed as a percentage of total foraging time, was <1% for day 1, 13% for day 2, and 37% for day 3 (P < 0.0001). Importantly, use of sagebrush by H3 and H increased steadily as the trial progressed, whereas use of sagebrush by L was consistently low (P < 0.05). Following conditioning, when lambs were tested at low stock densities during preference test 1, use of sagebrush did not differ by groups, but at higher stock densities in preference test 2, their use of sagebrush varied by treatments: H > H3 > L (P < 0.005). Thus, the availability of alternative foods, manipulated through animal density and the temporal allocation of those resources, both affected how readily lambs learned to use sagebrush.     

BIOLOGY OF THE BANK CORMORANT,PART 3: FORAGING BEHAVIOUR

Cooper, J. 1985. Biology of the Bank Cormorant, Part 3: Foraging behaviour. Ostrich 56: 86–95.

The Bank Cormorant Phalacrocorax neglectus, endemic to southern Africa, is primarily a solitary inshore forager. Bank Cormorants forage Primarily on the bottom among kelp beds but also may forage over shingle or coarse sand substrates or in midwater. Breeding birds forage up to 9 km from their colony. Little is known of foraging depth but birds may dive as deep as 28 m. Mean dive duration was 44,9 s and ratio of dives to surface rests was 2,18. In most cases prey is swallowed under water, presumably to avoid kleptoparasitism. Bank Cormorants foraged during daylight hours from before sunrise to after sunset. Birds did not forage in exceptionally rough seas. Mean female foraging bout duration (84,3 min) was significantly longer than that of males (68,4 min) in breeding individuals. Breeding males undertook significantly more foraging bouts (3,47 boutdday) than did females (3,02 bouts/day). No significant differences were found between the sexes when total time spent foraging/day by breeding birds was compared. It is not clear why males foraged more often, but for shorter periods, than did females, but the differences may be related to sexual dimorphism, males being larger than females.     

Grazing behaviour of dairy cows on biodiverse mountain pastures is more influenced by slope than cow breed

The aim of this study was to determine how cows with different genetic merit behave and perform when grazing biodiverse and heterogeneous mountain pastures with different slopes. Three groups of 12 cows in late lactation, each composed of four Holstein, four Montbéliarde and four Valdostana Red Pied cows, breeds of increasing presumed robustness and decreasing milk yield (MY) potential. Cows grazed without concentrate either on a low-diversity flat pasture or on two species-rich mountainous pastures having slopes of either 7° or 22°. Milk yield, BW and grazing behaviour were monitored two times in the first and once in the second grazing cycle. Cows of different breeds had similar behaviour on all pastures. The Montbéliarde cows performed close to their production potential; Holstein and Valdostana cows produced less milk than anticipated. No breed difference in terms of BW loss was found. The Valdostana cows exhibited the least selective behaviour with respect to plant species and plant growth stage. Still, all cows searched for the most palatable vegetation regardless of pasture diversity. On the steep pasture, cows optimised the trade-off between ingesting and saving energy to obtain feed. They remained longer at the lowest zone and selected forbs, whereas cows on the flatter pasture went to the upper zone to select grasses. The present study gave no evidence for a superior short-term adaptation to harsh grazing conditions through an optimised feeding behaviour of the Valdostana breed compared to Montbéliarde and Holstein cows.     

Plant species diversity and forage quality as affected by pasture management and simulated cattle activities

Grazed pastures have been historically used in Japan for animal production with little concern to biodiversity. However, pasturing has significant effects on biodiversity and productivity because it produces gaps in the distribution of vegetation due to animal activities. We hypothesized that different grazing activities would have effects on the diversity of plant species and forage quality in different ways and that the sward type would modify these effects. Therefore, we attempted to predict the diversity of plant species and changes in total nutrient content per area at the time since treatment on the basis of simulations of cattle activities in three pastures with different vegetation compositions. We created three ground types (grazed areas, cleared ground, and undisturbed areas) in three pastures (improved, partially improved semi-natural, and semi-natural pasture) and recorded the percentage cover of each plant within the plots. We repeatedly calculated the biodiversity indices from these community data by varying the sampling probabilities for each ground type, which provided us with the expected species diversity indices with the changing proportions of each ground type. Furthermore, we investigated the dry matter and forage qualities. For improved and partially improved semi-natural pasture, our models predicted that plant diversity increased as a saturating function of the proportion of cleared ground and grazed area relative to the undisturbed area, although our models also showed exponential curves for the semi-natural pasture. Forage samples from cleared ground plots and semi-natural pasture had the lowest forage quality among all pastures. Based on the predicted effects of cattle pasturing on the plant species biodiversity and forage quality, it may be more beneficial to maintain a small proportion of cleared ground in the improved pasture during intensive grazing.     

Influence of level of nutrition during late pregnancy on reproductive productivity of red deer I. Adult and primiparous hinds gestating red deer calves

The present study aimed to relate feed intake of red deer hinds during late pregnancy to dam body condition, foetal development and calf growth. Across 3 years, multiparous (n=33) or primiparous (n=18) hinds with known conception dates were housed in individual pens from days 150-220 of pregnancy, during which time they were each offered one of three daily allowances of pelletised rations (11 MJME/kg DM; 16% CP): high (H; ad libitum), medium (M; approximately 30% less; multiparous hinds only) and low (L; approximately 50% less). Restricted intake levels were retrospectively calculated from the mean intake of H hinds in the previous week. Hinds were returned to pasture at day 220 and calving was closely monitored. Liveweights, body condition score (BCS), and lactation score (LS) of hinds were recorded weekly from day 130 of pregnancy until calves were weaned at 12 weeks of age. Calves were tagged and weighed at birth, and subsequently weighed at 7 and 12 weeks of age. Additionally, hinds in the first year of study underwent CT scans on days 150 and 215 of pregnancy to assess compositional changes of the dam and conceptus. Mean daily ad libitum intakes of H hinds increased from 1.8 to 2.0 kg DM (0.6-0.7 MJME/kg0.75) at around day 150 to 2.8-3.2 kg DM (0.8-0.9 MJME/kg0.75) by day 220. Those of M and L hinds peaked at 1.8 and 1.6 kg DM, respectively, by day 220. This was reflected in significant treatment effects on liveweight gain and change in BCS and LS by the time of calving. CT scans indicated a significant treatment effect by day 215 on the mass of hind tissues (fat and lean) and a non-significant trend on conceptus/foetal weights. Despite apparent differences in foetal growth trajectories, there were no discernable treatment effects on sex-adjusted birth weights. However, there was an unexpectedly wide spread in calving dates that reflected considerable variation in gestation length. Furthermore, gestation length was negatively correlated with change in hind liveweight (but not BCS) between days 150 and 220 of pregnancy for all groups of hinds (P<0.05). Of three neonatal calf mortalities, none were related to overweight (dystocia) or underweight (non-viability) calves. Subsequent growth rates (g/day) of surviving calves did not reflect prior treatment of their dams, although variation in birth date influenced weights on specific dates. It is concluded from this study that while variation in nutrition to hinds during the last trimester may strongly influence foetal development, under conditions of modest feed imbalance, variation in gestation length compensates to ensure optimisation of birth weight.     

The influence of bite size on foraging at larger spatial and temporal scales by mammalian herbivores

Organisms respond to their heterogeneous environment in complex ways at many temporal and spatial scales. Here, I examine how the smallest scale process in foraging by mammalian herbivores, taking a bite, influences plants and herbivores over larger scales. First, because cropping bites competes with chewing them, bite size influences short-term intake rate of herbivores within plant patches. On the other hand, herbivores can chew bites while searching for new ones, thus influencing the time spent vigilant and intake rate as animals move among food patches. Therefore, bite size affects how much time herbivores must spend foraging each day. Because acquiring energy is necessary for fitness, herbivores recognize the importance of bite size and select bites, patches and diets based on tradeoffs between harvesting rates, digestion, and sheering forces. In turn, induced structural defenses of plants, such as thorns, allow plants to respond immediately to herbivory by reducing bite size and thus tissue loss. Over evolutionary time, herbivores have adapted mouth morphology that allows them to maximize bite size on their primary forage plant, whereas plants faced with large mammalian herbivores have adapted structures such as divarication that minimize bite size and protect themselves from herbivory. Finally, bite size available among plant communities can drive habitat segregation and migration of larger herbivores across landscapes.     

The gestation length of wapiti (Cervus elaphus) revisited

As an ancillary activity to an artificial insemination program in farmed wapiti, the length of gestation of 28 wapiti hinds that delivered single calves of established parentage was calculated. Estrus was synchronized in 47 wapiti using progesterone impregnated devices (controlled internal drug release, CIDR) and an injection of PMSG. All hinds were artificially inseminated between 60 and 63h after CIDR removal. Pregnancy was determined between 45 and 65 days by ultrasound. A verifiable figure for gestation length was obtained based both upon timed-artificial insemination, date of parturition, and confirmation of sire identity through microsatellite DNA technology. The calculated gestational length of 247 +/- 5 days was significantly (P < 0.0001) shorter than the generally quoted figure of 255 +/- 7 days.     

Impact of indoor feeding at late lactation stage on body reserves recovery and reproductive performances of Baladi dairy goats fed on pastoral system

Adaptive capacities of Baladi goats facing situations of food restrictions and re-feeding during lactation have been studied. Three diets were tested: mountain natural rangelands during early lactation, agricultural pastures during mid-lactation and indoor stall feeding during late lactation. Body weight (BW), body condition (BCS) and plasma metabolites (NEFA) as well as milk production (milk yield, milk fat and milk protein contents) were measured in the different feeding situations. Effect of late lactation re-feeding on reproduction was assessed through kids’ birth weight and weight gain from day 0 till day 60 of age. Results showed that on rangelands, goats’ body condition degraded, with initially fat goats loosing more weight and being subject to a greater reserves mobilization than lean ones. These expressed an adaptive behaviour through increasing their daily feed intake and by an intense body reserves replenishment following their transfer to the agricultural pastures and indoor feeding. In late lactation, even goats kept on agricultural pastures showed a similar reconstitution, showing the high priority of body reserves replenishment during late lactation whatever the feeding level. The milk rebounds observed showed a good reactivity from the Baladi goat in response to a feed improvement either on agricultural pasture or indoor. At the end of lactation the milk yield decreased in all feeding situations proving the priority given by the Baladi goats to the body reserves replenishment over the milk production in order to ensure the next cycle. However, even if there was no difference in kids’ birth weights, kids from stall-fed dams had higher weight gains between 0 and 60 days of age when compared to those from underfed ones.     

Effect of cattle grazing a species-rich mountain pasture under different stocking rates on the dynamics of diet selection and sward structure

Although stocking rate is a key management variable influencing the structure and composition of pastures, only few studies have simultaneously analysed the seasonal patterns of pasture use by cattle, and the adjustments the animals make to maintain intake of a high-quality diet over the grazing season. Therefore, over a 3-year study, we recorded diet selection, plot use and impact of heifers on sward structure and quality under three different stocking rates (0.6, 1.0 and 1.4 livestock units (LU) per ha) in a species-rich mountain pasture of central France. Measurements were made on three occasions between early June and the end of September each year. Overall, heifers selected for bites dominated by legumes or forbs, and against reproductive grass, whatever the stocking rate or season. Selection for tall mixed (P < 0.05), short mixed (P < 0.05) and short pure grass bites (P < 0.01) was more pronounced in plots grazed at the lowest stocking rate. Although heifers' selection for short patches decreased at the end of the season (P < 0.001), they continued to graze previously grazed areas, thus exhibiting a typical 'patch grazing' pattern, with the animals that grazed at the lowest stocking rate tending to better maintain their selection for short patches in September (treatment × period: P = 0.078). Neither diet quality nor individual animal performance were affected by the different stocking rate treatments despite high variability in the quantity and quality of herbage offered and differences in diet selection. However, at the 1.4 LU per ha stocking rate, the quantity of forage available per animal at the end of the season, 0.79 t dry matter (DM) per ha of green leaves with the median of sward height at 4.6 cm, approached levels limiting cattle's ability to compensate for the effects of increasing stocking rate. In plots grazed at 0.6 LU per ha, the total herbage biomass remained higher than 3 t DM per ha with more than 30% of plot area still covered by reproductive grass patches at the end of the grazing season, which in the medium term should affect the botanical composition of these pastures. Sward heterogeneity was high in plots grazed at 1.0 LU per ha, with sufficient herbage availability (1.1 t DM per ha of green leaves) to maintain animal performance, and more than 15% of plot area was kept at a reproductive stage at the end of the grazing season. Hence, it could represent the optimal balance to satisfy both livestock production and conservation management objectives.     

Configuration of daily grazing and searching of growing beef cattle in grassland: observational study

Many of the studies in Campos grasslands focus on management aspects such as the control of herbage allowance, and application of nutrients and/or overseeding with legumes. However, there is little literature on how the Campos grassland resource is utilised, especially regarding the grazing pattern and the relationship between pasture quantity and quality on daily grazing activities. The study of the ingestive behaviour in species-rich and heterogeneous native grasslands during daylight hours, and understanding how animals prioritise quality or quantity of intake in relation to pasture attributes, are important to comprehend the ingestive-digestive processes modulating the energy intake of animals and to achieve a better grazing management. Therefore, the objective was to describe and quantify the daily grazing behaviour of growing cattle grazing native pasture with different structures as a result of different management practices, and study the relationship of pasture attributes and intake through multivariate analysis. The study was carried out at the Faculty of Agronomy, Paysandú, Uruguay. Treatments were native grassland, overseeding with Trifolium pratense and Lotus tenuis + phosphorus, and native pasture + nitrogen-phosphorus. Grazing activities were discriminated into grazing, searching (defined when animals take 1–2 bites in one feeding station and then change to another feeding station and so on), ruminating and idling. The probability of time allocated to each activity was continuously measured during daylight hours (0700–1930) and was related to pasture structure and forage quality using regression tree models, while the bite rate was determined every 2 h. The diurnal pattern of growing cattle showed grazing and searching sessions, followed by ruminating and idling sessions. The length of sessions (as the probability of time allocated to each activity) varied throughout the day. The grazing probability was greater during afternoon than morning and midday (0.74 vs 0.45 vs 0.46, respectively), and it was associated with higher bite rate (34.2 bites/min). Regression tree models showed different grazing, searching and ruminating strategies according to pasture attributes. During the morning, animals modified grazing, searching, ruminating and idling strategies according to bite rate, crude protein in diet and herbage allowance. At midday, they only adjusted ruminating and idling, while during afternoon sessions, grazing activities were modified by pasture quantity attributes such as herbage mass and herbage allowance. By controlling the herbage allowance, herbage mass and pasture height, animals prioritise quality in the morning and quantity in the afternoon, integrating and modifying the grazing-searching and ruminating-idling pattern.