Determination of breeding strategies for beef cattle bull breeders selling bulls into two competing markets on a non-linear price grid

Computer simulation was used to suggest potential selection strategies for beef cattle breeders with different mixes of clients between two potential markets. The traditional market paid on the basis of carcass weight (CWT), while a new market considered marbling grade in addition to CWT as a basis for payment. Both markets instituted discounts for CWT in excess of 340 kg and light carcasses below 300 kg. Herds were simulated for each price category on the carcass weight grid for the new market. This enabled the establishment of phenotypic relationships among the traits examined [CWT, percent intramuscular fat (IMF), carcass value in the traditional market, carcass value in the new market, and the expected proportion of progeny in elite price cells in the new market pricing grid]. The appropriateness of breeding goals was assessed on the basis of client satisfaction. Satisfaction was determined by the equitable distribution of available stock between markets combined with the assessment of the utility of the animal within the market to which it was assigned. The best goal for breeders with predominantly traditional clients was a CWT in excess of 330 kg, while that for breeders with predominantly new market clients was a CWT of between 310 and 329 kg and with a marbling grade of AAA in the Ontario carcass pricing system. For breeders who wished to satisfy both new and traditional clients, the optimal CWT was 310-329 kg and the optimal marbling grade was AA-AAA. This combination resulted in satisfaction levels of greater than 75% among clients, regardless of the distribution of the clients between the traditional and new marketplaces.

Effect of restricted feed intake on early reproductive development in Large White gilts

Forty-five Large White gilts were used to study the effect of energy intake from 28 to 176 d of age on body composition and reproductive development. From 28 to 60 d, the gilts were fed ad libitum a 16.6 MJ DE/kg, 24% crude protein and 1.3% total lysine diet. From 61 d of age three dietary treatments were used; 1) ad libitum access to feed (15.6 MJ DE/kg, 21% crude protein and 1.07% total lysine) (H), 2) feed offered at 75% (M) of the previous days intake of H, and 3) feed offered at 60% (L) of the previous days intake of H. ADG from 61 to 176 d of age was (p <0.05) affected by treatment. Although live weight at 176 d of age did not differ (p >0.1) the H gilts had higher (p <0.08) carcass weights than the M or L gilts. Back fat depths were similar (p >0.1) for all treatments at 115 d of age, however by 176 d of age M and H gilts were fatter (p <0.1) than L gilts. The mean lipid deposition (LD) from 115 to 176 d of age for L gilts (78.9 g/d) was less (p <0.05) than for M gilts (143.6 g/d) and H gilts (135.6 g/d). There were no differences between treatments for protein deposition (PD) over the same period. More (p <0.05) H gilts (n=8) attained puberty (first observed estrus) than either M gilts or L gilts (n=4 for both). Follicle numbers were similar (p >0.1) across treatments. For gilts that attained puberty, H gilts had fewer (p <0.05) follicles (13.5) than M gilts (19.7) and L gilts (21.3). For gilts with follicular development, H gilts had the heaviest (458.7 g) reproductive tract weight (RTW). However, for those that attained puberty, L gilts had the heaviest RTW. RTW were lowest for those with no follicular development. Energy restriction had a negative impact on puberty attainment, i.e. it took longer to reach puberty. However, for gilts that attained puberty, the number of follicles was greater for those on lower feed intakes. It would appear that rate of fat deposition, but not necessarily the total amount of fat, plays an important role in puberty attainment.