Silva, A. L. | bioRxiv Science

bioRxiv2021

Intake, performance, and feeding behavior of Holstein and Holstein x Gyr heifers grazing intensive managed tropical grasses during the rainy season

Holstein x Gyr and Holstein are the primary dairy breed used in tropical systems, but when rearing under pasture, feed intake, behavior, and performance might differ between them. This study aimed to evaluate the voluntary intake, nutrient digestibility, performance, and ingestive behavior of Holstein and Holstein x Gyr ([1/2] Holstein x [1/2] Gyr) heifers managed in an intermittent grazing system of Guinea grass (Panicum maximum Jacq. cv. Mombaca). The experiment was conducted during the summer season throughout four periods of 21 d. Two 8-heifers (four Holstein and four Holstein x Gyr) groups, averaging 258.6 {+/-} 24.8 kg and 157.1 {+/-} 24.99 kg body weight, were used. Each group grazed a separate set of 16 paddocks, and all heifers received a concentrate supplement daily. Heifers were weighed at the beginning and end of the experiment. Fecal, forage and concentrate samples were evaluated for their dry matter (DM), crude protein (CP), crude fat, ash, neutral detergent fiber (NDF), and indigestible NDF. Feeding behavior was evaluated through 24 h of live observation for 48 h of each experimental period. Grazing, ruminating, resting, and intake of concentrate times were recorded, and rumination criteria, bout criteria, mealtime, meal frequency, and meal duration were estimated. There was no difference in dry matter intake (DMI). The Holstein x Gyr heifers had greater NDF intake and average daily gain (ADG), and feed efficiency tended to show greater CP and NDF digestibilities. The forage DMI of Holstein x Gyr was 11.70% greater than the Holstein heifers. Holstein grazed less than Holstein x Gyr heifers in the afternoon. Ruminating time was 18.43% lower for Holstein than Holstein x Gyr heifers, and rumination criteria were greater for Holstein heifers. Holstein heifers presented more prolonged rumination bouts and resting time than Holstein x Gyr heifers. Holstein x Gyr can ingest and ruminate greater amounts of fibrous material. Holstein heifers select lower fiber material, and they need to spend more time ruminating small portions of feed. Overall, we do not recommend using young Holstein heifers in tropical pasture conditions because their ADG is low because of its lower adaptability to fibrous feed and heat stress. However, this management condition is appropriate for Holstein x Gyr heifers and results in an adequate performance. ImplicationsThis study was the first to evaluate the performance and behavior of young Holstein x Gyr and Holsteins heifers in tropical grazing systems under the same nutritional and environmental conditions. Crossbreed and purebred heifers interacted differently with the pasture; however, without noticeable variation in grazing time. As expected, Holstein heifers performance in the tropical pasture was impaired by a reduction in intake and grazing time. The greater performance observed for Holstein x Gyr heifers was assigned to greater forage intake, rumination time, and efficient forage nutrient use, showing animals adaptability to management conditions.

zoology↗

bioRxiv2020

Digestive parameters during gestation of Holstein heifers

Our objective was to estimate nutrient intake, ruminal flow, total apparent and ruminal digestibility, rates of passage and digestion, ruminal and omasal pH, blood metabolite concentrations, and body measurements during gestation of Holstein heifers. Eleven pregnant Holstein heifers, 8 of which fitted with a rumen cannula (450 {+/-} 27.6 kg of body weight and 20 {+/-} 3.5 months of initial age) were used. All heifers received the same diet composed of corn silage, soybean meal, corn meal, minerals and vitamins, with a corn silage:concentrate ratio of 50:50 (on a dry matter basis), aiming an average daily gain of approximately 1.0 kg. The sampling periods were established according to the days of gestation: 145, 200, and 255 with a duration of 10 days per period. Total fecal samples were collected to estimate dry matter, organic matter, crude protein, and neutral detergent fiber digestibility. Blood samples were collected to analyze metabolites (non-esterified fatty acids, {beta}-hydroxybutyrate, urea, and glucose). Data were analyzed as a repeated measurements scheme, using MIXED procedure, with differences declared when P < 0.05. Dry matter intake expressed in kg/day increased from d-145 to d-200, and remaining stable until d-255 of gestation. The same results were observed for organic matter and crude protein intake, increasing 15.0 and 35.8% respectively. In contrast, when dry matter intake was evaluated as % body weight, we observed a decrease of 16.7% from d-200 to d-255. Days of gestation did not influence ruminal flow of dry matter, organic matter, crude protein, and neutral detergent fiber. We observed an increase in the ruminal digestibility of neutral detergent fiber by 20.5%. The apparent total-tract digestibility of dry matter, organic matter, and crude protein changed over days of gestation, with an increase of 11.9, 8.5, and 9.8%, respectively, when comparing d-145 with d-200. The rate of digestion of neutral detergent fiber increased from 2.0 to 3.5% h-1. Glucose levels decreased, while {beta}-hydroxybutirate and non-esterified fatty acids increased from d-145 to d-255. In conclusion, our results demonstrate a reduction in dry matter intake in % body weight due to pregnancy. It also shows an increase in total apparent digestibility through gestation, which imply a greater efficiency of use of nutrients by pregnant animals. Thus, further research is still needed to consolidate such results and to elucidate the mechanism about nutrient usage during the final third of gestation in heifers.

physiology↗