Energy and protein requirements of Holstein × Gyr crossbred heifers

Abstract

Nutrient requirements in cattle are dependent on physiological stage, breed and environmental conditions. In Holstein × Gyr crossbred dairy heifers, the lack of data remains a limiting factor for estimating energy and protein requirements. Thus, we aimed to estimate the energy and protein requirements of Holstein × Gyr crossbred heifers raised under tropical conditions. Twenty-two crossbred (½ Holstein × ½ Gyr) heifers with an average initial BW of 102.2 ± 3.4 kg and 3 to 4 months of age were used. To estimate requirements, the comparative slaughter technique was used: four animals were assigned to the reference group, slaughtered at the beginning of the experiment to estimate the initial empty BW (EBW) and composition of the animals that remained in the experiment. The remaining animals were randomized into three treatments based on targeted rates of BW gain: high (1.0 kg/day), low (0.5 kg/day) and close to maintenance (0.1 kg/day). At the end of the experiment, all animals were slaughtered to determine EBW, empty body gain (EBG) and body energy and protein contents. The linear regression parameters were estimated using PROC MIXED of SAS (version 9.4). Estimates of the parameters of non-linear regressions were adjusted through PROC NLIN of SAS using the Gauss–Newton method for parameter fit. The net requirements of energy for maintenance (NE m ) and metabolizable energy for maintenance (ME m ) were 0.303 and 0.469 MJ/EBW0.75 per day, respectively. The efficiency of use of ME m was 64.5%. The estimated equation to predict the net energy requirement for gain (NE g ) was: NE g (MJ/day) = 0.299 × EBW0.75 × EBG0.601. The efficiency of use of ME for gain (k g ) was 30.7%. The requirement of metabolizable protein for maintenance was 3.52 g/EBW0.75 per day. The equation to predict net protein requirement for gain (NP g ) was: NP g (g/day) = 243.65 × EBW−0.091 × EBG. The efficiency of use of metabolizable protein for gain (k) was 50.8%. We observed noteworthy differences when comparing to ME and protein requirements of Holstein × Gyr crossbred heifers with other systems. In addition, we also observed differences in estimates for NE m , NE g , NP g , k g and k. Therefore, we propose that the equations generated in the present study should be used to estimate energy and protein requirements for Holstein × Gyr crossbred dairy heifers raised in tropical conditions in the post-weaning phase up to 185 kg of BW.

Metabolizable Protein: 2. Requirements for Maintenance in Growing Saanen Goats

“…The overall k PG calculated (0.52 ± 0.0222) was close to the value reported to goats in AFRC ( 4 ) (0.59) but lower than that adopted by SCA ( 28 ) and NRC ( 1 ), in which both adopted 0.70. This value was also close to that of recent studies in dairy cows by Castro et al ( 29 ) of 0.51. Because the differences in protein content in tissue gain possibly affect this efficiency for growth ( 1 ), we would expect different values of k PG between sexes.…”

Feed Intake of Growing Dairy Heifers Raised under Tropical Conditions: A Model Evaluation Using Meta-Analysis

“…We used BW, SBW, and EBW for the comparisons previously described. For Jiao et al (2015) [95] and Moreira (2016) [86], we used SBW = 0.96 × BW [9] because in that study the NE m requirement values were expressed as BW 0.75 , but for Castro et al (2020) [96], we used EBW = 0.894 × SBW because the NE m requirement values were originally expressed as EBW 0.75 . Therefore, the low accuracy of predictions from the DMI model of NRC heifers could also be related to differences in NE m requirements and genetic variation in crossbred heifers.…”

“…However, a study suggested that NE m requirements of heifers increased over time, similar to cows [ 94 ], and estimated as 122 kcal/kg of SBW 0.75 for Holstein heifers from 6 to 22 months of age [ 95 ]. For crossbred Holstein × Gyr heifers, the requirement of NE m is suggested to be between 104 kcal/kg of SBW 0.75 (17 months and 1 / 2 Holstein × 1 / 2 Gyr) [ 86 ] and 67 kcal/kg of SBW 0.75 (3 to 7 months and 1 / 2 Holstein × 1 / 2 Gyr) [ 96 ]. We used BW, SBW, and EBW for the comparisons previously described.…”

“…Although important studies on the nutrient requirements of crossbred dairy cattle ( Bos taurus × Bos indicus ) have been published [ 96 , 97 , 98 ], data on heifers are still scarce. Since 2016, heifer studies have been performed to better understand the effects of ADG and supply of nutrients on mammary gland development in prepubertal and pubertal crossbred heifers [ 69 , 99 , 100 ].…”

The Potential of Using Temperate–Tropical Crossbreds and Agricultural by-Products, Associated with Heat Stress Management for Dairy Production in the Tropics: A Review

“…The breed’s performance in Southeast Asian countries ranges from 1710 to 1978 kg of milk/lactation [ 36 , 54 ]. Another well-established breed is the Holstein × Gyr breed, where several requirement and feed efficiency studies have been conducted in recent years [ 55 , 56 , 57 ]. The breed was observed to produce an average milk yield of 5118 and 5211 kg/lactation of 1/2 and 7/8 Holstein composition, respectively [ 38 ].…”