Subacute ruminal acidosis (SARA) was induced by replacing 25% of the total mixed ration intake [dry matter (DM) basis] with pellets consisting of 50% wheat and 50% barley. This reduced dietary forage content (DM basis) from 39.7 to 29.8% and increased the dietary concentrate content from 60.3 to 70.2%. Induction of SARA reduced the 24- and 48-h in situ neutral detergent fiber (NDF) degradabilities of grass hay numerically from 31.5% to 24.6% (P = 0.29) and from 51.3% to 36.9% (P < 0.05), respectively. The 24- and 48-h in situ NDF degradabilities of legume hay were reduced from 35.3 to 26.3% (P < 0.05) and from 49.0 to 35.8% (P < 0.05), respectively. The 24- and 48-h in situ NDF degradabilities of corn silage were reduced from 44.0 to 37.2% (P < 0.05) and from 56.1 to 44.8% (P < 0.05), respectively. This study suggests that induction of SARA by excess feeding of wheat/barley pellets reduces the rumen digestion of NDF from grass hay, legume hay, and corn silage.

Two hundred and forty Hubbard X Hubbard broiler breeders at 19 weeks of age were weight-sorted and transferred to individual laying cages where one of six experimental diets was provided to 41 weeks of age. Each diet was represented by 10 replicate groups of 4 individually caged and fed birds. Feed allocation was gradually increased to 150 g/bird per day, which provided 19 or 25 g crude protein and either 325, 385, or 450 kcal metabolizable energy (ME)/bird per day. Hens were inseminated every 7 days with .05 ml pooled semen from Hubbard males. Hen-day production was 1.6% lower with the high vs. low protein intake. Peak egg production occurred at 31 weeks and was 77.3, 87.9, and 84.1% for the low (L), medium (M), and high energy (H) intakes, respectively (P less than or equal to .01). Egg weight increased as the protein or energy intake increased; yolk content increased as energy intake increased or as broiler breeders aged (P less than or equal to .01). Carcass fat, protein, and moisture content of defeathered 41-week-old breeders were L: 45.5, 44.4, 56.6; M: 49.0, 40.4, 54.8; and H: 58.4, 32.5, 50.4, respectively (P less than or equal to .01). There were no dietary effects on hatchability, embryonic mortality, or fertility. From 32 to 35 weeks of age the higher protein intake increased egg weight by 1.2 g (P less than or equal to .05) and chick weight by .6 g; whereas hatched live chick weight was 39.6, 39.7, and 41.0, for L, M, and H diets, respectively (P less than or equal to .05).(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to evaluate the effect of feeding prepubertal heifers a diet containing a high level of polyunsaturated fatty acids on mammary development and milk production. A total of 116 Holstein heifers were either fed a conventionally formulated concentrate or a high oil (HO) concentrate, using the same formulation but including 20% soybean oil, from birth to 6 mo of age. After 6 mo of age, all heifers were managed identically. Mammary gland development was evaluated on heifers slaughtered at 4 mo (n = 10) and 12 mo (n = 30) of age. Other heifers were bred when they reached 15 mo of age and milk production and feed intake were recorded every day from wk 4 to 18 of lactation. Feeding the high oil concentrate increased the concentration of linoleic acid in blood plasma (176%) and mammary fat pad (78%) at 4 mo of age and mammary fat pad (93%) at 12 mo of age. At 4 mo of age, mammary development was similar in both treatments. At 12 mo of age, total, parenchyma, and stroma weights of the mammary gland were not affected by treatments. However, lipid content was lower and concentration of DNA was higher in the parenchyma of heifers fed the high oil diet. Nevertheless, total parenchymal DNA and dry fat free tissue content did not reach statistical significance despite the fact that they were, respectively, 15 and 21% higher in HO heifers. Milk production and composition was not affected by treatments. In conclusion, feeding prepubertal heifers with a high oil concentrate slightly improved the mammary development but effects were too small to be translated into better lactating performances.

This experiment determined the effects of dietary protein solubility on amount, form, and route of nitrogen loss in lactating Holstein dairy cows, and the ability of the Cornell Net Carbohydrate and Protein System (CNCPS) to accurately predict rumen microbial yield, serum urea N (SUN), milk urea N (MUN), and fecal N. Eighteen multiparous Holstein cows were assigned randomly to one of three dietary treatments that were similar in crude protein (17.7%) content but differed in their content of soluble intake protein (SIP). Dietary contents of SIP, as % of total CP were 30, 36, and 48%. The experimental period was 21 d, and total N balance collections were done during the last 5 d. As dietary content of SIP increased, excretion of urinary N increased quadratically, and it was the primary route of N excretion. Urinary excretion of purine derivatives (PD) responded quadratically as dietary SIP content increased. The CNCPS predicted a quadratic decrease in total metabolizable protein (MP) supply. No effect of dietary content of SIP was detected on MUN and SUN. The CNCPS predicted a quadratic decrease in SUN and MUN as dietary SIP increased. Results from this study indicated that changing the dietary content of SIP altered routes of N excretion in dairy cows, but had no effect on total N balance. The CNCPS did not adequately predict changes in SUN and MUN for cows fed diets varying in SIP.

The partitioning of AME intake (MEI) and recovered energy (RE; defined as MEI minus heat production) was investigated on Hubbard broiler-breeder hens (BB) by using indirect calorimetry and energy balance. The regression of RE on MEI was linear (R2 = .96; P less than .01) with a slope of .817 +/- .024 (SE) and a y-intercept of -238.3 +/- 10.7 (SE). The maintenance energy requirement was 292 kilojoule (kJ) per kg per day (367 kJ per kg.75 per day). The regression of body RE, defined as RE minus egg energy, on MEI was linear (R2 = .96; P less than .01) with a slope of .799 +/- .045 (SE) and a y-intercept of -344.9 +/- 19.7 (SE). Therefore, an MEI of 432 kJ per kg per day was required by BB hens to maintain body energy equilibrium when they were laying at approximately 85% production. At an MEI of less than 432 kJ per kg per day, body energy was used for egg production. The AME cost of depositing 1 kJ of body, egg, protein, or fat energy was (mean +/- SE) 1.21 +/- .06, 91 +/- .32, 1.96 +/- .71, and 1.05 +/- .15 kJ, respectively. The results indicate that individually caged BB hens between 28 and 36 wk of age in a thermal-neutral environment (21 C) require approximately 1.6 megajoule (MJ) of AME per bird per day for normal growth (3 g/per day) and egg production (85%).

. 2005. Lactation response of cows to different levels of ruminally inert conjugated linoleic acids under commercial conditions. Can. J. Anim. Sci. 85: 231-242. Dietary conjugated linoleic acid (CLA) supplements have been shown to reduce milk fat synthesis in dairy cows. A rumen-inert source of CLA is required for commercial feed applications. The conversion of dietary lipids to a calcium salt is considered as a method to counter the extensive hydrogenation of dietary lipids that occurs in the rumen. Our objective was to determine whether feeding calcium salts of CLA under commercial conditions would affect milk production, milk composition and blood metabolic profile. A total of 240 dairy cows from eight farms were blocked according to the calving date, and randomly assigned to four treatments providing CLA at 0, 8, 16 and 32 g d -1 . Milk production was recorded and milk was sampled on day 0, 7, 14, 28 and 42 of the feeding period. Blood samples were taken on day 42 from early-lactating cows (< 157 d in milk) to determine the metabolic profile. Milk fat yield was decreased 11, 20 and 28%, and milk fat concentration was reduced 13, 22 and 28% (linear; P < 0.001) when cows received 8, 16 and 32 g d -1 of CLA, respectively. Milk yield, milk protein and blood metabolic parameters were not affected by experimental treatments. Calcium salts of CLA can be used as an effective tool to manage milk fat content on commercial dairy farms. dans l'alimentation diminue la synthèse du gras du lait chez la vache. Les ALC alimentaires peuvent cependant être hydrogénés par les microorganismes du rumen. La formation de sels de calcium est considérée comme une méthode pour prévenir l'hydrogénation des ALC au cours de leur passage dans le rumen. Afin de déterminer les effets des ALC sous forme inerte sur la production et la composition du lait et sur le profil métabolique sanguin en conditions commerciales, 240 vaches laitières ont été réparties selon un dispositif en blocs, selon la date de vêlage. Les traitements consistaient en quatre différentes doses d'ALC (0, 8, 16 et 32 g j -1 ) distribuées de façon aléatoire à l'intérieur de chaque bloc. La production laitière a été enregistrée et des échantillons de lait ont été recueillis aux j 0, 7, 14, 28 et 42. Des échantillons sanguins ont été prélevés au j 42. La production de gras a été diminuée de 11, 20 et 28%, et la teneur en gras diminuée de 13, 22 et 28% par rapport au témoin lorsque les animaux ont reçu 8, 16 et 32 g j -1 d'ALC (linéaire, P < 0,001). La production laitière, la production et la teneur en protéine du lait et les paramètres sanguins n'ont pas été affectés. Les sels de calcium d'ALC pourraient être utilisés en conditions commerciales pour contrôler efficacement la teneur en gras du lait.

Conjugated linoleic acid (CLA) has the potential to be used as a dietary means of manipulating milk fat production of dairy cows to meet specified short-term targets, as in a supply-managed industry. An experiment was conducted to evaluate the dose-response to calcium salts of CLA fed as a top-dress on a corn- and alfalfa-based TMR. In two 5 × 5 Latin squares of 28-d periods, five primiparous and five multiparous cows were fed 0, 22, 45, 67 or 178 g d-1 CLA (29% trans-10, cis-12) as a calcium salt. Results from one multiparous cow on the 178 g d-1 treatment were removed from statistical analysis because milk production fell to 1.2 kg d-1 by the end of the period. On average, milk, lactose and protein yields increased at the lower doses of CLA and decreased to control levels at the highest dose. Milk fat yield declined progressively from 876 to 770, 689, 676 and 543 g d-1 on the five doses. Net energy balance of cows increased linearly from -1.5 Mcal d-1 on the control to 2.0 Mcal d-1 at 178 g d-1 CLA. The percentage depression in milk fat yield at different doses of trans-10, cis-12 CLA was described by the equation y = 54/(1 + 22.8/dose). Comparison with published literature suggested that feeding calcium salts of CLA was 30% as effective in depressing milk fat production as an abomasal infusion, due to rumen biohydrogenation and intestinal indigestibility.Key words: Milk composition, cattle, diet

Two hundred and forty individually caged Hubbard x Hubbard broiler breeders (BB) were fed one of six diets at 150 g/bird per day, which provided 19 or 25 g protein and 325, 385, or 450 kcal nitrogen-corrected metabolizable energy. In Trial 1, chicks hatched from 29-wk-old BB were sexed and 12 females and 12 males placed in each of four replicate floor pens per treatment. A 23% crude protein (CP) starter (0 to 20 day), 20% CP grower (21 to 34 day) and 18% CP finisher (35 to 41 day) diets were fed. Protein intake of BB had no effect on body weight of offspring. Energy intake of BB had no effect on growth of female offspring; however body weights of 20 day-old-male offspring were 575, 586, and 601 g for low, medium, and high energy intake, respectively (P less than or equal to .01). Increasing BB energy intake increased carcass protein and reduced fat in male offspring (P less than or equal to .01) and decreased the percentage of Canada Grade B ratings for both sexes (P less than or equal to .05). In Trials 2 to 4, chicks from BB at 32, 36, and 40 wk were sexed and cage-reared to 21 days of age. The energy intake of BB had no effect on female offspring growth. Male offspring weighed 570, 563, and 585 g for the low, medium, and high energy intakes, respectively (P less than or equal to .01).