Effects of freestall vs. bedded pack housing on growth performance, health status, and behavioral responses of weaned heifers.

This research evaluates the effect of two housing types, freestalls vs. bedded-pack, on growth performance, health scoring, and behavior of weaned heifers. Twenty-four heifers with no previous experience with freestalls (12 heifers/ treatment) were randomly assigned to the two treatments (freestalls vs. bedded-pack) at d 80 ± 3 of age. Heifers had free access to total mixed ration (TMR) and water throughout the experiment. The TMR intake and health score were recorded daily from d 80 to 110 of age. Body weight and skeletal growth of heifers were measured at the beginning (d 80) and the end (d110) of the experiment. Feeding behaviors were recorded for a period of 22 h and at the same time. Growth performance (ADG, structural growth, and final body weight), overall DMI, and health assessment (fecal score, general appearance, and rectal temperature) were similar between treatments. Behavioral patterns of eating, drinking, standing, lying, and rumination were also similar between treatments. However, in freestall-housed heifers, the proportion of time spent lying inside the stall increased by 8.1%, and time spent lying outside the stall decreased by 9.44% from the beginning to the end of the study (from 80 to 110 d). In summary, our results indicate that weaned heifers showed similar growth performance, behavior, and health when housed in freestall and bedded-pack housing. However, introducing weaned heifers to freestall housing at an early age will prepare them for using the facility.

The effects of the ratio of pellets of wheat and barley grains to ground corn grain in the diet on sorting and chewing activities of heat stressed dairy cows.

BACKGROUND: Normal feeding behaviours is one of the criteria of the health condition of dairy cows particularly in the condition of heat stress. OBJECTIVE: The study evaluated the effects of the ratio of pellets of wheat and barley grains to ground corn grain on sorting activity and chewing behaviour of lactating dairy cows managed under ambient conditions including natural heat stress events. MATERIALS AND METHODS: Nine multiparous cows (650 ± 56 kg Body Weight; mean ± SD) averaging 102 ± 13 days in milk and producing 54 ± 6 kg/d were randomly assigned to a triplicate 3 × 3 Latin square. During each 21-d period, cows received one of three total mixed rations as dietary treatments. The dietary treatments were three ratio of pellets (containing 50% ground wheat and 50% ground barley): ground corn on a dry matter (DM) basis: 1) 33.3:66.6 (low); 2) 66.6:33.3 (medium); and 3) 100:0 (high). During the experiment, the ambient temperature-humidity index was equal or more than 72, indicating that the cows were predisposed to heat stress condition. RESULTS: Increasing the proportion of wheat-barley pellets in the diet had a minimal effect on sorting index of different particles during the first 6 h of the day. However, later in the day (6-18h), sorting against long particles (particles >19 mm) and in favour of fine particles (particles <1.18 mm) linearly increased with increasing the proportion of pellet; as a result overall daily sorting against long particles was increased with increasing the proportion of pellets. Although the average of daily eating and rumination was not affected by the treatments in the day times with high ambient THI, time spent for eating and rumination was low and eating time had more fluctuation for diet contained a high level of pellets. CONCLUSION: Increasing the proportion of pellets of barley and wheat grains in the diet under conditions of heat stress caused more fluctuation in daily eating behaviour and cows were predisposed to sort against long particles.

The origin of N isotopic discrimination and its relationship with feed efficiency in fattening yearling bulls is diet-dependent.

Nitrogen (N) isotopic discrimination (i.e. the difference in natural 15N abundance between the animal proteins and the diet; Δ15N) is known to correlate with N use efficiency (NUE) and feed conversion efficiency (FCE) in ruminants. However, results from the literature are not always consistent across studies, likely due to isotopic discrimination pathways that may differ with the nature of diets. The objective of the present study was to assess at which level, from rumen to tissues, Δ15N originates and becomes related to NUE and FCE in fattening yearling bulls when they are fed two contrasted diets. Twenty-four Charolais yearling bulls were randomly divided into two groups and fed during 8 months, from weaning to slaughter, either 1) a high starch diet based on corn silage supplying a balanced N to energy ratio at the rumen level (starch) or 2) a high fiber diet based on grass silage supplying an excess of rumen degradable N (fiber). All animals were slaughtered and samples of different digestive pools (ruminal, duodenal, ileal and fecal contents), animal tissues (duodenum, liver and muscle), blood and urine were collected for each animal. Ruminal content was further used to isolate liquid-associated bacteria (LAB), protozoa and free ammonia, while plasma proteins were obtained from blood. All samples along with feed were analyzed for their N isotopic composition. For both diets, the digestive contribution (i.e. the N isotopic discrimination occurring before absorption) to the Δ15N observed in animal tissues accounted for 65 ± 11%, leaving only one third to the contribution of post-absorptive metabolism. Concerning the Δ15N in digestive pools, the majority of these changes occurred in the rumen (av. Δ15N = 2.12 ± 0.66‰), with only minor 15N enrichments thereafter (av. Δ15N = 2.24 ± 0.41‰), highlighting the key role of the rumen on N isotopic discrimination. A strong, significant overall relationship (n = 24) between Δ15N and FCE or NUE was found when using any post-absorptive metabolic pool (duodenum, liver, or muscle tissues, or plasma proteins; 0.52 < r < 0.73; P ≤ 0.01), probably as these pools reflect both digestive and post-absorptive metabolic phenomena. Fiber diet compared to starch diet had a lower feed efficiency and promoted higher (P ≤ 0.05) Δ15N values across all post-absorptive metabolic pools and some digestive pools (ruminal, duodenal, and ileal contents). The within-diet relationship (n = 12) between Δ15N and feed efficiency was not as strong and consistent as the overall relationship, with contrasted responses between the two diets for specific pools (diet x pool interaction; P ≤ 0.01). Our results highlight the contrasted use of N at the rumen level between the two experimental diets and suggests the need for different equations to predict FCE or NUE from Δ15N according to the type of diet. In conclusion, rumen digestion and associated microbial activity can play an important role on N isotopic discrimination so rumen effect related to diet may interfere with the relationship between Δ15N and feed efficiency in fattening yearling bulls.