An international group of researchers from Brazil and the US examined the use of different nutritional strategies pre- and post-weaning to anticipate the age of puberty in beef heifers. They published their results in the journal of Livestock Science.
“Research on the effect of nutrition on puberty in Nellore heifers are scarce, and it is not known that kind of supplementation may affect puberty,” they said. “The objective of this study was to evaluate the impact of three nutritional strategies (pre-partum dam supplementation, creep-feeding and post-weaning feedlot) on age at puberty in Nellore heifers.”
The group found that supplementing dam diets pre-partum or creep feeding did not change heifers’ age at puberty or body weight, and that there were no interactions between the supplementation stages, they said. But, later supplementation influenced puberty timing.
“The post-weaning feedlot treatment anticipated the age at puberty,” said members of the research team. “At 18 months of age, the percentage of pubertal heifers was increased by post-weaning feedlot (31.7 vs. 13.3%;) and led to an increase of 10% in pregnancy rate at the same age.”
Why supplemental nutrition?
The majority of the Brazilian beef cattle herd is comprised of Nellore cattle on pasture, but the production system can mean that heifers do not reach their potential productive and reproductive ability as pasture quality is seasonally variable, said the researchers.
“This factor is one of those that are responsible for the late age of puberty and first pregnancy in Brazilian herds,” they said. “The delayed age at first calving decreases lifetime production per cows, and increases the proportion of farm resources that must be dedicated to nonproductive animals.”
Previous researchers have examined supplementation in beef cattle to hasten puberty with minimum cost, said researchers. But more work is needed to understand which kinds of nutritional supplementation may alter puberty timing.
“The last trimester of gestation and post-weaning are the periods that calves may experience undernutrition in pasture systems, and before weaning (creep-feeding) is a period in which weight gain of calves can be enhanced,” they said. “These situations may cause metabolic or endocrine imprinting in heifers that are able to influence productive and reproductive parameters.”
Researchers examined three nutritional systems in the study with three periods of supplementation – pre-partum dam supplementation with protein at 0.5kg soybean meal per cow per day for the last trimester of gestation; creep feeding with 22% crude protein (CP) and 72% total digestible nutrients (TDN) for 95 days before weaning; and, in the third period, post-weaning feedlot from seven to 11 months, with 17% CP and 58% TDN, said the researchers.
All three groups were compared with cattle in the same period of life that did not receive the supplemental feed, creep feed or were on pasture only instead of a feedlot diet, they said.
Cows and heifers were weighed at the start of each new supplementation period, they said. And heifers were checked monthly for signs of puberty after reaching 240kg.
No interactions were found among the different types of supplementation for the variables analyzed, said the researchers.
“Neither the cow supplementation nor creep feeding used in the present study anticipated puberty in Nellore heifers,” they said. “However, enhanced nutrition during the post-weaning period was an effective method to anticipate puberty.”
Pre-partum supplements raised the percentage of cyclic cows by about 73 days post-partum and increased the body weight (BW) of cows at weaning, but did not alter variables for the heifer calves, they said.
At weaning, calves that were given the pre-partum dam supplementation or creep-feeding had similar BW compared to the non-supplemented heifers, said the researchers.
However, at the end of the post-weaning period heifers on the feedlot supplement had a greater body weight than those on just pasture, they said. “Post-weaning feedlot feeding increased the BW of heifers from eight until 26 month of age, and heifers under feedlot were 44 and 8 kg heavier than heifers on pasture at 11 (end of feedlot) and 26 months of age, respectively,” they added.
Additionally, the first two dietary treatments, dam supplementation and creep-feed, did not alter when heifers hit puberty, they said. But, the feedlot diet did move forward the time for puberty and increased the amount of heifers that reached puberty by 18 months.
Source: Livestock Science
Title: Effect of pre-partum dam supplementation, creep-feeding and post-weaning feedlot on age at puberty in Nellore heifers
Authors: Delci Nepomuceno, Alexandre Pires, Marcos Ferraz Junior, Marcos Biehl, Jose Gonçalves, Elizangela Moreira, Michael Day