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Agricultural Advances
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This is an Open Access Journal

Open Access journal
ISSN (Print) 2251-7820
Published by Sjournals

[11 journals]

Determinants of birth weight and its size as an onset representative of
growth potential in goat and sheep meat production
- Authors: Never Assan
  Pages: 522 - 536
  Abstract: Birth weight is an important growth trait in goats and sheep which is of remarkable productive and economic interest for efficient meat production. Birth size in goats and sheep follows the pattern of prenatal growth and development, which is determined by genetics and a variety of environmental factors. Information on determinants of birth weight is of concern to producers, over and above the animal breeders, because birth weight has much influence on kid/lamb weaning weight hence later the overall flocks’ meat production. Paternal and maternal genotypes are important sources of variation on birth weight in goats and sheep. By way of illustration apart from breed effect, environmental factors influencing birth weight include nutrition, dam age and parity, season and year, sex and birth type. These factors and their interactive forces proffer the overall impression as explanatory variables for birth weight variation in goats and sheep. Males have superior birth weight as compared to females and this can be perpetuated up until weaning age. The kidding/lambing season greatly influence birth weight due to its bearing on availability of forage, hence it is suggested that mating schedules for dams should be designed in a manner where pregnancies should coincide with adequate grazing in order to attain optimal birth size. The differential pattern of feed resources from season to season or month to another might affect dam’s nutrition throughout their pregnancy consequently the birth outcome. Kids/lambs of primiparous ewes/does have a birth weight disadvantage, hence producers should consider alternatives for managing underweight birth on an individual flock basis. A pronounced effect of litter size, with compromised birth size in kids/lambs born as triplets being lower as compared with those born as twins, which in turn is lower than that in kids/lambs born as singles. Interactions of determinants of birth weight are important in goats and sheep namely breed by parity, breed by birth type and birth type by parity. The point to note is that birth weight is highly correlated to anticipated future weights until mature or slaughter weight which can presumably influence meat production. An understanding of the determinants of birth weight will warrant modifications in the breeding and management schedules to minimize influences, which reduce meat production efficiency. The present review is undertaken to give an insight on the determinants of birth weight for instance age of dam, type of birth, sex, year and month of birth.
  PubDate: 2020-05-20
  Issue No: Vol. 9, No. 5 (2020)
Weaning age/time based model influencing performance in goats and sheep
meat production
- Authors: Never Assan
  Pages: 537 - 544
  Abstract: Weaning is an essential animal husbandry intervention which has been associated with nutritional stress that interferes with both animal’s behavioral and physiological responses consequently influencing post weaning growth performance in goats and sheep production. The timing of weaning and/or weaning age of kids/lambs becomes critical in determination of flock performance with the intention of maximizing meat productivity and improving profitability. There are two possibilities that exist in deciding on weaning age of kids/lambs, thus early and late weaning, however, the decision on when to wean is dependent mainly on the production environment and purpose, as well as the dam welfare. Age at weaning differ greatly in sheep and goats, therefrom 14 days to natural weaning, and exceeding four months of age. In sheep production effective early weaning has been practiced untimely at 14 days; in goats’ kids have been weaned early successfully at 28 days. Early weaning is considered traditionally weaning ahead of the 90 days of age; 60 days is most widely used; age thereafter qualifies for late weaning. The age at weaning greatly influences post weaning animal performance, however if not timed properly it would impact negatively also on weaner survival rates. Weaning itself is a very stressful procedure and subjecting kids/lambs to further stress which directly impinge on the kid/lamb’s immunity consequently increasing their susceptibility to diseases and reduced weight gain. There is need for age of weaning to balance the potential positive impacts on the ewes/does to rebreed, with potential negative impacts on the kid/lamb growth performance and survivability. Early weaning has become an effective husbandry practice especially in advanced goat and sheep production systems, which focuses on shortened female breeding reproductive cycle, while enhancing meat productivity through increased frequency of kidding/lambing. It is important to consider weaning age in relation to nutritional strategies which provide adequate time for diet transition which is intended not to compromise feed utilization and feed conversion efficiency in kids/lambs consequently reducing growth performance. The effectiveness of weaning age and anticipated live weight gains post-weaning is dependent on nutritional management especially concentrate supplementation which may promote performance and productivity in pastured based systems. Late weaning is probably convenient for less prolific goat and sheep breeds and genotypes not selected for their growth potential. It should be acknowledged that there is interaction between weaning age with other factors such as nutrition, sex and weight of animal. Some of the goat and sheep producers worldwide have shifted to use of weight based weaning model, similar age but with different weights, heavier lambs have superior development efficiency during lactation. The present review gives an insight on the consequences of early and late weaning on animal’s post weaning performance in small ruminants.
  PubDate: 2020-05-20
  Issue No: Vol. 9, No. 5 (2020)